xref: /libCEED/examples/fluids/navierstokes.c (revision 1bb4263918babe26a363fff2527ef14c0f7af2a5)

// Copyright (c) 2017, Lawrence Livermore National Security, LLC. Produced at
// the Lawrence Livermore National Laboratory. LLNL-CODE-734707. All Rights
// reserved. See files LICENSE and NOTICE for details.
//
// This file is part of CEED, a collection of benchmarks, miniapps, software
// libraries and APIs for efficient high-order finite element and spectral
// element discretizations for exascale applications. For more information and
// source code availability see http://github.com/ceed.
//
// The CEED research is supported by the Exascale Computing Project 17-SC-20-SC,
// a collaborative effort of two U.S. Department of Energy organizations (Office
// of Science and the National Nuclear Security Administration) responsible for
// the planning and preparation of a capable exascale ecosystem, including
// software, applications, hardware, advanced system engineering and early
// testbed platforms, in support of the nation's exascale computing imperative.

//                        libCEED + PETSc Example: Navier-Stokes
//
// This example demonstrates a simple usage of libCEED with PETSc to solve a
// Navier-Stokes problem.
//
// The code is intentionally "raw", using only low-level communication
// primitives.
//
// Build with:
//
//     make [PETSC_DIR=</path/to/petsc>] [CEED_DIR=</path/to/libceed>] navierstokes
//
// Sample runs:
//
//     ./navierstokes -ceed /cpu/self -problem density_current -degree_volume 1
//     ./navierstokes -ceed /gpu/occa -problem advection -degree_volume 1
//
//TESTARGS -ceed {ceed_resource} -test -degree_volume 1

/// @file
/// Navier-Stokes example using PETSc

const char help[] = "Solve Navier-Stokes using PETSc and libCEED\n";

#include <petscts.h>
#include <petscdmplex.h>
#include <ceed.h>
#include <stdbool.h>
#include <petscsys.h>
#include "common.h"
#include "setup-boundary.h"
#include "advection.h"
#include "advection2d.h"
#include "densitycurrent.h"

// Problem Options
typedef enum {
  NS_DENSITY_CURRENT = 0,
  NS_ADVECTION = 1,
  NS_ADVECTION2D = 2,
} problemType;
static const char *const problemTypes[] = {
  "density_current",
  "advection",
  "advection2d",
  "problemType","NS_",0
};

typedef enum {
  STAB_NONE = 0,
  STAB_SU = 1,   // Streamline Upwind
  STAB_SUPG = 2, // Streamline Upwind Petrov-Galerkin
} StabilizationType;
static const char *const StabilizationTypes[] = {
  "NONE",
  "SU",
  "SUPG",
  "StabilizationType", "STAB_", NULL
};

// Problem specific data
typedef struct {
  CeedInt dim, qdatasizeVol;
  CeedQFunctionUser setupVol, setupSur, ics, applyVol_rhs, applySur_rhs,
                    applyVol_ifunction, applySur_ifunction;
  PetscErrorCode (*bc)(PetscInt, PetscReal, const PetscReal[], PetscInt,
                       PetscScalar[], void *);
  const char *setupVol_loc, *setupSur_loc, *ics_loc, *applyVol_rhs_loc,
             *applySur_rhs_loc, *applyVol_ifunction_loc, *applySur_ifunction_loc;
  const bool non_zero_time;
} problemData;

problemData problemOptions[] = {
  [NS_DENSITY_CURRENT] = {
    .dim                       = 3,
    .qdatasizeVol              = 10,
    .setupVol                  = Setup,
    .setupVol_loc              = Setup_loc,
    .setupSur                  = SetupBoundary,
    .setupSur_loc              = SetupBoundary_loc,
    .ics                       = ICsDC,
    .ics_loc                   = ICsDC_loc,
    .applyVol_rhs              = DC,
    .applyVol_rhs_loc          = DC_loc,
  //.applySur_rhs              = DC_Sur,
  //.applySur_rhs_loc          = DC_Sur_loc,
    .applyVol_ifunction        = IFunction_DC,
    .applyVol_ifunction_loc    = IFunction_DC_loc,
  //.applySur_ifunction        = IFunction_DC_Sur,
  //.applySur_ifunction_loc    = IFunction_DC_Sur_loc,
    .bc                        = Exact_DC,
    .non_zero_time             = false,
  },
  [NS_ADVECTION] = {
    .dim                       = 3,
    .qdatasizeVol              = 10,
    .setupVol                  = Setup,
    .setupVol_loc              = Setup_loc,
    .setupSur                  = SetupBoundary,
    .setupSur_loc              = SetupBoundary_loc,
    .ics                       = ICsAdvection,
    .ics_loc                   = ICsAdvection_loc,
    .applyVol_rhs              = Advection,
    .applyVol_rhs_loc          = Advection_loc,
  //.applySur_rhs              = Advection_Sur,
  //.applySur_rhs_loc          = Advection_Sur_loc,
    .applyVol_ifunction        = IFunction_Advection,
    .applyVol_ifunction_loc    = IFunction_Advection_loc,
  //.applySur_ifunction        = IFunction_Advection_Sur,
  //.applySur_ifunction_loc    = IFunction_Advection_Sur_loc,
    .bc                        = Exact_Advection,
    .non_zero_time             = true,
  },
  [NS_ADVECTION2D] = {
    .dim                       = 2,
    .qdatasizeVol              = 5,
    .setupVol                  = Setup2d,
    .setupVol_loc              = Setup2d_loc,
    .setupSur                  = SetupBoundary2d,
    .setupSur_loc              = SetupBoundary2d_loc,
    .ics                       = ICsAdvection2d,
    .ics_loc                   = ICsAdvection2d_loc,
    .applyVol_rhs              = Advection2d,
    .applyVol_rhs_loc          = Advection2d_loc,
    .applySur_rhs              = Advection2d_Sur,
    .applySur_rhs_loc          = Advection2d_Sur_loc,
    .applyVol_ifunction        = IFunction_Advection2d,
    .applyVol_ifunction_loc    = IFunction_Advection2d_loc,
  //.applySur_ifunction        = IFunction_Advection2d_Sur,
  //.applySur_ifunction_loc    = IFunction_Advection2d_Sur_loc,
    .bc                        = Exact_Advection2d,
    .non_zero_time             = true,
  },
};

// PETSc user data
typedef struct User_ *User;
typedef struct Units_ *Units;

struct User_ {
  MPI_Comm comm;
  PetscInt outputfreq;
  DM dm;
  DM dmviz;
  Mat interpviz;
  Ceed ceed;
  Units units;
  CeedVector qceed, qdotceed, gceed;
  CeedOperator op_rhs_vol, op_rhs_sur, op_rhs,
               op_ifunction_vol, op_ifunction_sur, op_ifunction;
  Vec M;
  char outputfolder[PETSC_MAX_PATH_LEN];
  PetscInt contsteps;
};

struct Units_ {
  // fundamental units
  PetscScalar meter;
  PetscScalar kilogram;
  PetscScalar second;
  PetscScalar Kelvin;
  // derived units
  PetscScalar Pascal;
  PetscScalar JperkgK;
  PetscScalar mpersquareds;
  PetscScalar WpermK;
  PetscScalar kgpercubicm;
  PetscScalar kgpersquaredms;
  PetscScalar Joulepercubicm;
};

typedef struct SimpleBC_ *SimpleBC;
struct SimpleBC_ {
  PetscInt nwall, nslip[3];
  PetscInt walls[10], slips[3][10];
};

// Essential BC dofs are encoded in closure indices as -(i+1).
static PetscInt Involute(PetscInt i) {
  return i >= 0 ? i : -(i+1);
}

// Utility function to create local CEED restriction
static PetscErrorCode CreateRestrictionFromPlex(Ceed ceed, DM dm, CeedInt P,
    CeedInt height, DMLabel domainLabel, CeedInt value,
    CeedElemRestriction *Erestrict) {

  PetscSection   section;
  PetscInt       p, Nelem, Ndof, *erestrict, eoffset, nfields, dim,
                 depth;
  DMLabel depthLabel;
  IS depthIS, iterIS;
  const PetscInt *iterIndices;
  PetscErrorCode ierr;
  Vec Uloc;

  PetscFunctionBeginUser;
  ierr = DMGetDimension(dm, &dim); CHKERRQ(ierr);
  ierr = DMGetLocalSection(dm,&section); CHKERRQ(ierr);
  ierr = PetscSectionGetNumFields(section, &nfields); CHKERRQ(ierr);
  PetscInt ncomp[nfields], fieldoff[nfields+1];
  fieldoff[0] = 0;
  for (PetscInt f=0; f<nfields; f++) {
    ierr = PetscSectionGetFieldComponents(section, f, &ncomp[f]); CHKERRQ(ierr);
    fieldoff[f+1] = fieldoff[f] + ncomp[f];
  }

  ierr = DMPlexGetDepth(dm, &depth); CHKERRQ(ierr);
  ierr = DMPlexGetDepthLabel(dm, &depthLabel); CHKERRQ(ierr);
  ierr = DMLabelGetStratumIS(depthLabel, depth - height, &depthIS); CHKERRQ(ierr);
  if (domainLabel) {
    IS domainIS;
    ierr = DMLabelGetStratumIS(domainLabel, value, &domainIS); CHKERRQ(ierr);
    ierr = ISIntersect(depthIS, domainIS, &iterIS); CHKERRQ(ierr);
    ierr = ISDestroy(&domainIS); CHKERRQ(ierr);
    ierr = ISDestroy(&depthIS); CHKERRQ(ierr);
  } else {
    iterIS = depthIS;
  }
  ierr = ISGetLocalSize(iterIS, &Nelem); CHKERRQ(ierr);
  ierr = ISGetIndices(iterIS, &iterIndices); CHKERRQ(ierr);
  ierr = PetscMalloc1(Nelem*PetscPowInt(P, dim), &erestrict); CHKERRQ(ierr);
  for (p=0,eoffset=0; p<Nelem; p++) {
    PetscInt c = iterIndices[p];
    PetscInt numindices, *indices, nnodes;
    ierr = DMPlexGetClosureIndices(dm, section, section, c, &numindices,
                                   &indices, NULL); CHKERRQ(ierr);
    if (numindices % fieldoff[nfields])
      SETERRQ1(PETSC_COMM_SELF, PETSC_ERR_ARG_INCOMP,
               "Number of closure indices not compatible with Cell %D", c);
    nnodes = numindices / fieldoff[nfields];
    for (PetscInt i=0; i<nnodes; i++) {
      // Check that indices are blocked by node and thus can be coalesced as a single field with
      // fieldoff[nfields] = sum(ncomp) components.
      for (PetscInt f=0; f<nfields; f++) {
        for (PetscInt j=0; j<ncomp[f]; j++) {
          if (Involute(indices[fieldoff[f]*nnodes + i*ncomp[f] + j])
              != Involute(indices[i*ncomp[0]]) + fieldoff[f] + j)
            SETERRQ4(PETSC_COMM_SELF,PETSC_ERR_ARG_INCOMP,
                     "Cell %D closure indices not interlaced for node %D field %D component %D",
                     c, i, f, j);
        }
      }
      // Essential boundary conditions are encoded as -(loc+1), but we don't care so we decode.
      PetscInt loc = Involute(indices[i*ncomp[0]]);
      erestrict[eoffset++] = loc;
    }
    ierr = DMPlexRestoreClosureIndices(dm, section, section, c, &numindices,
                                       &indices, NULL); CHKERRQ(ierr);
  }
  if (eoffset != Nelem*PetscPowInt(P, dim))
    SETERRQ3(PETSC_COMM_SELF, PETSC_ERR_LIB,
             "ElemRestriction of size (%D,%D) initialized %D nodes", Nelem,
             PetscPowInt(P, dim),eoffset);
  ierr = ISRestoreIndices(iterIS, &iterIndices); CHKERRQ(ierr);
  ierr = ISDestroy(&iterIS); CHKERRQ(ierr);

  ierr = DMGetLocalVector(dm, &Uloc); CHKERRQ(ierr);
  ierr = VecGetLocalSize(Uloc, &Ndof); CHKERRQ(ierr);
  ierr = DMRestoreLocalVector(dm, &Uloc); CHKERRQ(ierr);
  CeedElemRestrictionCreate(ceed, Nelem, PetscPowInt(P, dim), fieldoff[nfields],
                            1, Ndof, CEED_MEM_HOST, CEED_COPY_VALUES, erestrict,
                            Erestrict);
  ierr = PetscFree(erestrict); CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

// Utility function to get Ceed Restriction for each domain
static PetscErrorCode GetRestrictionForDomain(Ceed ceed, DM dm, CeedInt ncompx, CeedInt dim,
    CeedInt height, DMLabel domainLabel, CeedInt value, CeedInt P, CeedInt Q,
    CeedInt qdatasize, CeedElemRestriction *restrictq,
    CeedElemRestriction *restrictx, CeedElemRestriction *restrictqdi) {

  DM dmcoord;
  CeedInt localNelem;
  CeedInt Qdim = CeedIntPow(Q, dim);
  PetscErrorCode ierr;

  PetscFunctionBeginUser;
  ierr = DMGetCoordinateDM(dm, &dmcoord); CHKERRQ(ierr);
  ierr = DMPlexSetClosurePermutationTensor(dmcoord, PETSC_DETERMINE, NULL);
  CHKERRQ(ierr);
  ierr = CreateRestrictionFromPlex(ceed, dm, P, height, domainLabel, value, restrictq);
  CHKERRQ(ierr);
  ierr = CreateRestrictionFromPlex(ceed, dmcoord, 2, height, domainLabel, value, restrictx);
  CHKERRQ(ierr);
  CeedElemRestrictionGetNumElements(*restrictq, &localNelem);
  CeedElemRestrictionCreateStrided(ceed, localNelem, Qdim,
                                   qdatasize, qdatasize*localNelem*Qdim,
                                   CEED_STRIDES_BACKEND, restrictqdi);
  PetscFunctionReturn(0);
}

static int CreateVectorFromPetscVec(Ceed ceed, Vec p, CeedVector *v) {
  PetscErrorCode ierr;
  PetscInt m;

  PetscFunctionBeginUser;
  ierr = VecGetLocalSize(p, &m); CHKERRQ(ierr);
  ierr = CeedVectorCreate(ceed, m, v); CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

static int VectorPlacePetscVec(CeedVector c, Vec p) {
  PetscErrorCode ierr;
  PetscInt mceed,mpetsc;
  PetscScalar *a;

  PetscFunctionBeginUser;
  ierr = CeedVectorGetLength(c, &mceed); CHKERRQ(ierr);
  ierr = VecGetLocalSize(p, &mpetsc); CHKERRQ(ierr);
  if (mceed != mpetsc) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_ARG_INCOMP,
                                  "Cannot place PETSc Vec of length %D in CeedVector of length %D",mpetsc,mceed);
  ierr = VecGetArray(p, &a); CHKERRQ(ierr);
  CeedVectorSetArray(c, CEED_MEM_HOST, CEED_USE_POINTER, a);
  PetscFunctionReturn(0);
}

static PetscErrorCode DMPlexInsertBoundaryValues_NS(DM dm,
    PetscBool insertEssential, Vec Qloc, PetscReal time, Vec faceGeomFVM,
    Vec cellGeomFVM, Vec gradFVM) {
  PetscErrorCode ierr;
  Vec Qbc;

  PetscFunctionBegin;
  ierr = DMGetNamedLocalVector(dm, "Qbc", &Qbc); CHKERRQ(ierr);
  ierr = VecAXPY(Qloc, 1., Qbc); CHKERRQ(ierr);
  ierr = DMRestoreNamedLocalVector(dm, "Qbc", &Qbc); CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

// This is the RHS of the ODE, given as u_t = G(t,u)
// This function takes in a state vector Q and writes into G
static PetscErrorCode RHS_NS(TS ts, PetscReal t, Vec Q, Vec G, void *userData) {
  PetscErrorCode ierr;
  User user = *(User *)userData;
  PetscScalar *q, *g;
  Vec Qloc, Gloc;

  // Global-to-local
  PetscFunctionBeginUser;
  ierr = DMGetLocalVector(user->dm, &Qloc); CHKERRQ(ierr);
  ierr = DMGetLocalVector(user->dm, &Gloc); CHKERRQ(ierr);
  ierr = VecZeroEntries(Qloc); CHKERRQ(ierr);
  ierr = DMGlobalToLocal(user->dm, Q, INSERT_VALUES, Qloc); CHKERRQ(ierr);
  ierr = DMPlexInsertBoundaryValues(user->dm, PETSC_TRUE, Qloc, 0.0,
                                    NULL, NULL, NULL); CHKERRQ(ierr);
  ierr = VecZeroEntries(Gloc); CHKERRQ(ierr);

  // Ceed Vectors
  ierr = VecGetArrayRead(Qloc, (const PetscScalar **)&q); CHKERRQ(ierr);
  ierr = VecGetArray(Gloc, &g); CHKERRQ(ierr);
  CeedVectorSetArray(user->qceed, CEED_MEM_HOST, CEED_USE_POINTER, q);
  CeedVectorSetArray(user->gceed, CEED_MEM_HOST, CEED_USE_POINTER, g);

  // Apply CEED operator
  CeedOperatorApply(user->op_rhs, user->qceed, user->gceed,
                    CEED_REQUEST_IMMEDIATE);

  // Restore vectors
  ierr = VecRestoreArrayRead(Qloc, (const PetscScalar **)&q); CHKERRQ(ierr);
  ierr = VecRestoreArray(Gloc, &g); CHKERRQ(ierr);

  ierr = VecZeroEntries(G); CHKERRQ(ierr);
  ierr = DMLocalToGlobal(user->dm, Gloc, ADD_VALUES, G); CHKERRQ(ierr);

  // Inverse of the lumped mass matrix
  ierr = VecPointwiseMult(G, G, user->M); // M is Minv
  CHKERRQ(ierr);

  ierr = DMRestoreLocalVector(user->dm, &Qloc); CHKERRQ(ierr);
  ierr = DMRestoreLocalVector(user->dm, &Gloc); CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

static PetscErrorCode IFunction_NS(TS ts, PetscReal t, Vec Q, Vec Qdot, Vec G,
                                   void *userData) {
  PetscErrorCode ierr;
  User user = *(User *)userData;
  const PetscScalar *q, *qdot;
  PetscScalar *g;
  Vec Qloc, Qdotloc, Gloc;

  // Global-to-local
  PetscFunctionBeginUser;
  ierr = DMGetLocalVector(user->dm, &Qloc); CHKERRQ(ierr);
  ierr = DMGetLocalVector(user->dm, &Qdotloc); CHKERRQ(ierr);
  ierr = DMGetLocalVector(user->dm, &Gloc); CHKERRQ(ierr);
  ierr = VecZeroEntries(Qloc); CHKERRQ(ierr);
  ierr = DMGlobalToLocal(user->dm, Q, INSERT_VALUES, Qloc); CHKERRQ(ierr);
  ierr = DMPlexInsertBoundaryValues(user->dm, PETSC_TRUE, Qloc, 0.0,
                                    NULL, NULL, NULL); CHKERRQ(ierr);
  ierr = VecZeroEntries(Qdotloc); CHKERRQ(ierr);
  ierr = DMGlobalToLocal(user->dm, Qdot, INSERT_VALUES, Qdotloc); CHKERRQ(ierr);
  ierr = VecZeroEntries(Gloc); CHKERRQ(ierr);

  // Ceed Vectors
  ierr = VecGetArrayRead(Qloc, &q); CHKERRQ(ierr);
  ierr = VecGetArrayRead(Qdotloc, &qdot); CHKERRQ(ierr);
  ierr = VecGetArray(Gloc, &g); CHKERRQ(ierr);
  CeedVectorSetArray(user->qceed, CEED_MEM_HOST, CEED_USE_POINTER,
                     (PetscScalar *)q);
  CeedVectorSetArray(user->qdotceed, CEED_MEM_HOST, CEED_USE_POINTER,
                     (PetscScalar *)qdot);
  CeedVectorSetArray(user->gceed, CEED_MEM_HOST, CEED_USE_POINTER, g);

  // Apply CEED operator
  CeedOperatorApply(user->op_ifunction, user->qceed, user->gceed,
                    CEED_REQUEST_IMMEDIATE);

  // Restore vectors
  ierr = VecRestoreArrayRead(Qloc, &q); CHKERRQ(ierr);
  ierr = VecRestoreArrayRead(Qdotloc, &qdot); CHKERRQ(ierr);
  ierr = VecRestoreArray(Gloc, &g); CHKERRQ(ierr);

  ierr = VecZeroEntries(G); CHKERRQ(ierr);
  ierr = DMLocalToGlobal(user->dm, Gloc, ADD_VALUES, G); CHKERRQ(ierr);

  ierr = DMRestoreLocalVector(user->dm, &Qloc); CHKERRQ(ierr);
  ierr = DMRestoreLocalVector(user->dm, &Qdotloc); CHKERRQ(ierr);
  ierr = DMRestoreLocalVector(user->dm, &Gloc); CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

// User provided TS Monitor
static PetscErrorCode TSMonitor_NS(TS ts, PetscInt stepno, PetscReal time,
                                   Vec Q, void *ctx) {
  User user = ctx;
  Vec Qloc;
  char filepath[PETSC_MAX_PATH_LEN];
  PetscViewer viewer;
  PetscErrorCode ierr;

  // Set up output
  PetscFunctionBeginUser;
  // Print every 'outputfreq' steps
  if (stepno % user->outputfreq != 0)
    PetscFunctionReturn(0);
  ierr = DMGetLocalVector(user->dm, &Qloc); CHKERRQ(ierr);
  ierr = PetscObjectSetName((PetscObject)Qloc, "StateVec"); CHKERRQ(ierr);
  ierr = VecZeroEntries(Qloc); CHKERRQ(ierr);
  ierr = DMGlobalToLocal(user->dm, Q, INSERT_VALUES, Qloc); CHKERRQ(ierr);

  // Output
  ierr = PetscSNPrintf(filepath, sizeof filepath, "%s/ns-%03D.vtu",
                       user->outputfolder, stepno + user->contsteps);
  CHKERRQ(ierr);
  ierr = PetscViewerVTKOpen(PetscObjectComm((PetscObject)Q), filepath,
                            FILE_MODE_WRITE, &viewer); CHKERRQ(ierr);
  ierr = VecView(Qloc, viewer); CHKERRQ(ierr);
  if (user->dmviz) {
    Vec Qrefined, Qrefined_loc;
    char filepath_refined[PETSC_MAX_PATH_LEN];
    PetscViewer viewer_refined;

    ierr = DMGetGlobalVector(user->dmviz, &Qrefined); CHKERRQ(ierr);
    ierr = DMGetLocalVector(user->dmviz, &Qrefined_loc); CHKERRQ(ierr);
    ierr = PetscObjectSetName((PetscObject)Qrefined_loc, "Refined");
    CHKERRQ(ierr);
    ierr = MatInterpolate(user->interpviz, Q, Qrefined); CHKERRQ(ierr);
    ierr = VecZeroEntries(Qrefined_loc); CHKERRQ(ierr);
    ierr = DMGlobalToLocal(user->dmviz, Qrefined, INSERT_VALUES, Qrefined_loc);
    CHKERRQ(ierr);
    ierr = PetscSNPrintf(filepath_refined, sizeof filepath_refined,
                         "%s/nsrefined-%03D.vtu",
                         user->outputfolder, stepno + user->contsteps);
    CHKERRQ(ierr);
    ierr = PetscViewerVTKOpen(PetscObjectComm((PetscObject)Qrefined),
                              filepath_refined,
                              FILE_MODE_WRITE, &viewer_refined); CHKERRQ(ierr);
    ierr = VecView(Qrefined_loc, viewer_refined); CHKERRQ(ierr);
    ierr = DMRestoreLocalVector(user->dmviz, &Qrefined_loc); CHKERRQ(ierr);
    ierr = DMRestoreGlobalVector(user->dmviz, &Qrefined); CHKERRQ(ierr);
    ierr = PetscViewerDestroy(&viewer_refined); CHKERRQ(ierr);
  }
  ierr = PetscViewerDestroy(&viewer); CHKERRQ(ierr);
  ierr = DMRestoreLocalVector(user->dm, &Qloc); CHKERRQ(ierr);

  // Save data in a binary file for continuation of simulations
  ierr = PetscSNPrintf(filepath, sizeof filepath, "%s/ns-solution.bin",
                       user->outputfolder); CHKERRQ(ierr);
  ierr = PetscViewerBinaryOpen(user->comm, filepath, FILE_MODE_WRITE, &viewer);
  CHKERRQ(ierr);
  ierr = VecView(Q, viewer); CHKERRQ(ierr);
  ierr = PetscViewerDestroy(&viewer); CHKERRQ(ierr);

  // Save time stamp
  // Dimensionalize time back
  time /= user->units->second;
  ierr = PetscSNPrintf(filepath, sizeof filepath, "%s/ns-time.bin",
                       user->outputfolder); CHKERRQ(ierr);
  ierr = PetscViewerBinaryOpen(user->comm, filepath, FILE_MODE_WRITE, &viewer);
  CHKERRQ(ierr);
  #if PETSC_VERSION_GE(3,13,0)
  ierr = PetscViewerBinaryWrite(viewer, &time, 1, PETSC_REAL);
  #else
  ierr = PetscViewerBinaryWrite(viewer, &time, 1, PETSC_REAL, true);
  #endif
  CHKERRQ(ierr);
  ierr = PetscViewerDestroy(&viewer); CHKERRQ(ierr);

  PetscFunctionReturn(0);
}

static PetscErrorCode ICs_PetscMultiplicity(CeedOperator op_ics,
    CeedVector xcorners, CeedVector q0ceed, DM dm, Vec Qloc, Vec Q,
    CeedElemRestriction restrictq, SetupContext ctxSetup, CeedScalar time) {
  PetscErrorCode ierr;
  CeedVector multlvec;
  Vec Multiplicity, MultiplicityLoc;

  ctxSetup->time = time;
  ierr = VecZeroEntries(Qloc); CHKERRQ(ierr);
  ierr = VectorPlacePetscVec(q0ceed, Qloc); CHKERRQ(ierr);
  CeedOperatorApply(op_ics, xcorners, q0ceed, CEED_REQUEST_IMMEDIATE);
  ierr = VecZeroEntries(Q); CHKERRQ(ierr);
  ierr = DMLocalToGlobal(dm, Qloc, ADD_VALUES, Q); CHKERRQ(ierr);

  // Fix multiplicity for output of ICs
  ierr = DMGetLocalVector(dm, &MultiplicityLoc); CHKERRQ(ierr);
  CeedElemRestrictionCreateVector(restrictq, &multlvec, NULL);
  ierr = VectorPlacePetscVec(multlvec, MultiplicityLoc); CHKERRQ(ierr);
  CeedElemRestrictionGetMultiplicity(restrictq, multlvec);
  CeedVectorDestroy(&multlvec);
  ierr = DMGetGlobalVector(dm, &Multiplicity); CHKERRQ(ierr);
  ierr = VecZeroEntries(Multiplicity); CHKERRQ(ierr);
  ierr = DMLocalToGlobal(dm, MultiplicityLoc, ADD_VALUES, Multiplicity);
  CHKERRQ(ierr);
  ierr = VecPointwiseDivide(Q, Q, Multiplicity); CHKERRQ(ierr);
  ierr = VecPointwiseDivide(Qloc, Qloc, MultiplicityLoc); CHKERRQ(ierr);
  ierr = DMRestoreLocalVector(dm, &MultiplicityLoc); CHKERRQ(ierr);
  ierr = DMRestoreGlobalVector(dm, &Multiplicity); CHKERRQ(ierr);

  PetscFunctionReturn(0);
}

static PetscErrorCode ComputeLumpedMassMatrix(Ceed ceed, DM dm,
    CeedElemRestriction restrictq, CeedBasis basisq,
    CeedElemRestriction restrictqdi, CeedVector qdata, Vec M) {
  PetscErrorCode ierr;
  CeedQFunction qf_mass;
  CeedOperator op_mass;
  CeedVector mceed;
  Vec Mloc;
  CeedInt ncompq, qdatasize;

  PetscFunctionBeginUser;
  CeedElemRestrictionGetNumComponents(restrictq, &ncompq);
  CeedElemRestrictionGetNumComponents(restrictqdi, &qdatasize);
  // Create the Q-function that defines the action of the mass operator
  CeedQFunctionCreateInterior(ceed, 1, Mass, Mass_loc, &qf_mass);
  CeedQFunctionAddInput(qf_mass, "q", ncompq, CEED_EVAL_INTERP);
  CeedQFunctionAddInput(qf_mass, "qdata", qdatasize, CEED_EVAL_NONE);
  CeedQFunctionAddOutput(qf_mass, "v", ncompq, CEED_EVAL_INTERP);

  // Create the mass operator
  CeedOperatorCreate(ceed, qf_mass, NULL, NULL, &op_mass);
  CeedOperatorSetField(op_mass, "q", restrictq, basisq, CEED_VECTOR_ACTIVE);
  CeedOperatorSetField(op_mass, "qdata", restrictqdi,
                       CEED_BASIS_COLLOCATED, qdata);
  CeedOperatorSetField(op_mass, "v", restrictq, basisq, CEED_VECTOR_ACTIVE);

  ierr = DMGetLocalVector(dm, &Mloc); CHKERRQ(ierr);
  ierr = VecZeroEntries(Mloc); CHKERRQ(ierr);
  CeedElemRestrictionCreateVector(restrictq, &mceed, NULL);
  ierr = VectorPlacePetscVec(mceed, Mloc); CHKERRQ(ierr);

  {
    // Compute a lumped mass matrix
    CeedVector onesvec;
    CeedElemRestrictionCreateVector(restrictq, &onesvec, NULL);
    CeedVectorSetValue(onesvec, 1.0);
    CeedOperatorApply(op_mass, onesvec, mceed, CEED_REQUEST_IMMEDIATE);
    CeedVectorDestroy(&onesvec);
    CeedOperatorDestroy(&op_mass);
    CeedVectorDestroy(&mceed);
  }
  CeedQFunctionDestroy(&qf_mass);

  ierr = VecZeroEntries(M); CHKERRQ(ierr);
  ierr = DMLocalToGlobal(dm, Mloc, ADD_VALUES, M); CHKERRQ(ierr);
  ierr = DMRestoreLocalVector(dm, &Mloc); CHKERRQ(ierr);

  // Invert diagonally lumped mass vector for RHS function
  ierr = VecReciprocal(M); CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

PetscErrorCode SetUpDM(DM dm, problemData *problem, PetscInt degree,
                       SimpleBC bc, void *ctxSetup) {
  PetscErrorCode ierr;

  PetscFunctionBeginUser;
  {
    // Configure the finite element space and boundary conditions
    PetscFE fe;
    PetscSpace fespace;
    PetscInt ncompq = 5;
    ierr = PetscFECreateLagrange(PETSC_COMM_SELF, problem->dim, ncompq,
                                 PETSC_FALSE, degree, PETSC_DECIDE,
                                 &fe); CHKERRQ(ierr);
    ierr = PetscObjectSetName((PetscObject)fe, "Q"); CHKERRQ(ierr);
    ierr = DMAddField(dm,NULL,(PetscObject)fe); CHKERRQ(ierr);
    ierr = DMCreateDS(dm); CHKERRQ(ierr);
    /* Wall boundary conditions are zero velocity and zero flux for density and energy */
    {
      PetscInt comps[3] = {1, 2, 3};
      ierr = DMAddBoundary(dm, DM_BC_ESSENTIAL, "wall", "Face Sets", 0,
                           3, comps, (void(*)(void))problem->bc,
                           bc->nwall, bc->walls, ctxSetup); CHKERRQ(ierr);
    }
    {
      PetscInt comps[1] = {1};
      ierr = DMAddBoundary(dm, DM_BC_ESSENTIAL, "slipx", "Face Sets", 0,
                           1, comps, (void(*)(void))NULL, bc->nslip[0],
                           bc->slips[0], ctxSetup); CHKERRQ(ierr);
      comps[0] = 2;
      ierr = DMAddBoundary(dm, DM_BC_ESSENTIAL, "slipy", "Face Sets", 0,
                           1, comps, (void(*)(void))NULL, bc->nslip[1],
                           bc->slips[1], ctxSetup); CHKERRQ(ierr);
      comps[0] = 3;
      ierr = DMAddBoundary(dm, DM_BC_ESSENTIAL, "slipz", "Face Sets", 0,
                           1, comps, (void(*)(void))NULL, bc->nslip[2],
                           bc->slips[2], ctxSetup); CHKERRQ(ierr);
    }
    ierr = DMPlexSetClosurePermutationTensor(dm, PETSC_DETERMINE,NULL);
    CHKERRQ(ierr);
    ierr = PetscFEGetBasisSpace(fe, &fespace); CHKERRQ(ierr);
    ierr = PetscFEDestroy(&fe); CHKERRQ(ierr);
  }
  {
    // Empty name for conserved field (because there is only one field)
    PetscSection section;
    ierr = DMGetLocalSection(dm, &section); CHKERRQ(ierr);
    ierr = PetscSectionSetFieldName(section, 0, ""); CHKERRQ(ierr);
    ierr = PetscSectionSetComponentName(section, 0, 0, "Density");
    CHKERRQ(ierr);
    ierr = PetscSectionSetComponentName(section, 0, 1, "MomentumX");
    CHKERRQ(ierr);
    ierr = PetscSectionSetComponentName(section, 0, 2, "MomentumY");
    CHKERRQ(ierr);
    ierr = PetscSectionSetComponentName(section, 0, 3, "MomentumZ");
    CHKERRQ(ierr);
    ierr = PetscSectionSetComponentName(section, 0, 4, "EnergyDensity");
    CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}

int main(int argc, char **argv) {
  PetscInt ierr;
  MPI_Comm comm;
  DM dm, dmcoord, dmviz, dmvizfine;
  Mat interpviz;
  TS ts;
  TSAdapt adapt;
  User user;
  Units units;
  char ceedresource[4096] = "/cpu/self";
  PetscInt localNelemVol, localNelemSur, lnodes, steps;
  const PetscInt ncompq = 5;
  PetscMPIInt rank;
  PetscScalar ftime;
  Vec Q, Qloc, Xloc;
  Ceed ceed;
  CeedInt numP_Vol, numP_Sur, numQ_Vol, numQ_Sur;
  CeedVector xcorners, qdataVol, qdataSur, q0ceedVol, q0ceedSur;
  CeedBasis basisxVol, basisxcVol, basisqVol, basisxSur, basisxcSur, basisqSur;
  CeedElemRestriction restrictxVol, restrictqVol, restrictqdiVol,
                      restrictxSur, restrictqSur, restrictqdiSur;
  CeedQFunction qf_setupVol, qf_setupSur, qf_ics, qf_rhsVol, qf_rhsSur,
                qf_ifunctionVol, qf_ifunctionSur;
  CeedOperator op_setupVol, op_setupSur, op_ics;
  CeedScalar Rd;
  PetscScalar WpermK, Pascal, JperkgK, mpersquareds, kgpercubicm,
              kgpersquaredms, Joulepercubicm;
  problemType problemChoice;
  problemData *problem = NULL;
  StabilizationType stab;
  PetscBool   test, implicit;
  PetscInt    viz_refine = 0;
  struct SimpleBC_ bc = {
    .nwall = 6,
    .walls = {1,2,3,4,5,6},
  };
  double start, cpu_time_used;

  // Create the libCEED contexts
  PetscScalar meter     = 1e-2;     // 1 meter in scaled length units
  PetscScalar second    = 1e-2;     // 1 second in scaled time units
  PetscScalar kilogram  = 1e-6;     // 1 kilogram in scaled mass units
  PetscScalar Kelvin    = 1;        // 1 Kelvin in scaled temperature units
  CeedScalar theta0     = 300.;     // K
  CeedScalar thetaC     = -15.;     // K
  CeedScalar P0         = 1.e5;     // Pa
  CeedScalar N          = 0.01;     // 1/s
  CeedScalar cv         = 717.;     // J/(kg K)
  CeedScalar cp         = 1004.;    // J/(kg K)
  CeedScalar g          = 9.81;     // m/s^2
  CeedScalar lambda     = -2./3.;   // -
  CeedScalar mu         = 75.;      // Pa s, dynamic viscosity
  // mu = 75 is not physical for air, but is good for numerical stability
  CeedScalar k          = 0.02638;  // W/(m K)
  CeedScalar CtauS      = 0.;       // dimensionless
  CeedScalar strong_form = 0.;      // [0,1]
  PetscScalar lx        = 8000.;    // m
  PetscScalar ly        = 8000.;    // m
  PetscScalar lz        = 4000.;    // m
  CeedScalar rc         = 1000.;    // m (Radius of bubble)
  PetscScalar resx      = 1000.;    // m (resolution in x)
  PetscScalar resy      = 1000.;    // m (resolution in y)
  PetscScalar resz      = 1000.;    // m (resolution in z)
  PetscInt outputfreq   = 10;       // -
  PetscInt contsteps    = 0;        // -
  PetscInt degreeVol    = 1;        // -
  PetscInt degreeSur    = 1;        // -
  PetscInt qextraVol    = 2;        // -
  PetscInt qextraSur    = 2;        // -
  DMBoundaryType periodicity[] = {DM_BOUNDARY_NONE, DM_BOUNDARY_NONE,
                                  DM_BOUNDARY_NONE
                                 };
  PetscReal center[3], dc_axis[3] = {0, 0, 0};

  ierr = PetscInitialize(&argc, &argv, NULL, help);
  if (ierr) return ierr;

  // Allocate PETSc context
  ierr = PetscCalloc1(1, &user); CHKERRQ(ierr);
  ierr = PetscMalloc1(1, &units); CHKERRQ(ierr);

  // Parse command line options
  comm = PETSC_COMM_WORLD;
  ierr = PetscOptionsBegin(comm, NULL, "Navier-Stokes in PETSc with libCEED",
                           NULL); CHKERRQ(ierr);
  ierr = PetscOptionsString("-ceed", "CEED resource specifier",
                            NULL, ceedresource, ceedresource,
                            sizeof(ceedresource), NULL); CHKERRQ(ierr);
  ierr = PetscOptionsBool("-test", "Run in test mode",
                          NULL, test=PETSC_FALSE, &test, NULL); CHKERRQ(ierr);
  problemChoice = NS_DENSITY_CURRENT;
  ierr = PetscOptionsEnum("-problem", "Problem to solve", NULL,
                          problemTypes, (PetscEnum)problemChoice,
                          (PetscEnum *)&problemChoice, NULL); CHKERRQ(ierr);
  problem = &problemOptions[problemChoice];
  ierr = PetscOptionsEnum("-stab", "Stabilization method", NULL,
                          StabilizationTypes, (PetscEnum)(stab = STAB_NONE),
                          (PetscEnum *)&stab, NULL); CHKERRQ(ierr);
  ierr = PetscOptionsBool("-implicit", "Use implicit (IFunction) formulation",
                          NULL, implicit=PETSC_FALSE, &implicit, NULL);
  CHKERRQ(ierr);
  {
    PetscInt len;
    PetscBool flg;
    ierr = PetscOptionsIntArray("-bc_wall",
                                "Use wall boundary conditions on this list of faces",
                                NULL, bc.walls,
                                (len = sizeof(bc.walls) / sizeof(bc.walls[0]),
                                 &len), &flg); CHKERRQ(ierr);
    if (flg) bc.nwall = len;
    for (PetscInt j=0; j<3; j++) {
      const char *flags[3] = {"-bc_slip_x", "-bc_slip_y", "-bc_slip_z"};
      ierr = PetscOptionsIntArray(flags[j],
                                  "Use slip boundary conditions on this list of faces",
                                  NULL, bc.slips[j],
                                  (len = sizeof(bc.slips[j]) / sizeof(bc.slips[j][0]),
                                   &len), &flg);
      CHKERRQ(ierr);
      if (flg) bc.nslip[j] = len;
    }
  }
  ierr = PetscOptionsInt("-viz_refine",
                         "Regular refinement levels for visualization",
                         NULL, viz_refine, &viz_refine, NULL);
  CHKERRQ(ierr);
  ierr = PetscOptionsScalar("-units_meter", "1 meter in scaled length units",
                            NULL, meter, &meter, NULL); CHKERRQ(ierr);
  meter = fabs(meter);
  ierr = PetscOptionsScalar("-units_second","1 second in scaled time units",
                            NULL, second, &second, NULL); CHKERRQ(ierr);
  second = fabs(second);
  ierr = PetscOptionsScalar("-units_kilogram","1 kilogram in scaled mass units",
                            NULL, kilogram, &kilogram, NULL); CHKERRQ(ierr);
  kilogram = fabs(kilogram);
  ierr = PetscOptionsScalar("-units_Kelvin",
                            "1 Kelvin in scaled temperature units",
                            NULL, Kelvin, &Kelvin, NULL); CHKERRQ(ierr);
  Kelvin = fabs(Kelvin);
  ierr = PetscOptionsScalar("-theta0", "Reference potential temperature",
                            NULL, theta0, &theta0, NULL); CHKERRQ(ierr);
  ierr = PetscOptionsScalar("-thetaC", "Perturbation of potential temperature",
                            NULL, thetaC, &thetaC, NULL); CHKERRQ(ierr);
  ierr = PetscOptionsScalar("-P0", "Atmospheric pressure",
                            NULL, P0, &P0, NULL); CHKERRQ(ierr);
  ierr = PetscOptionsScalar("-N", "Brunt-Vaisala frequency",
                            NULL, N, &N, NULL); CHKERRQ(ierr);
  ierr = PetscOptionsScalar("-cv", "Heat capacity at constant volume",
                            NULL, cv, &cv, NULL); CHKERRQ(ierr);
  ierr = PetscOptionsScalar("-cp", "Heat capacity at constant pressure",
                            NULL, cp, &cp, NULL); CHKERRQ(ierr);
  ierr = PetscOptionsScalar("-g", "Gravitational acceleration",
                            NULL, g, &g, NULL); CHKERRQ(ierr);
  ierr = PetscOptionsScalar("-lambda",
                            "Stokes hypothesis second viscosity coefficient",
                            NULL, lambda, &lambda, NULL); CHKERRQ(ierr);
  ierr = PetscOptionsScalar("-mu", "Shear dynamic viscosity coefficient",
                            NULL, mu, &mu, NULL); CHKERRQ(ierr);
  ierr = PetscOptionsScalar("-k", "Thermal conductivity",
                            NULL, k, &k, NULL); CHKERRQ(ierr);
  ierr = PetscOptionsScalar("-CtauS",
                            "Scale coefficient for tau (nondimensional)",
                            NULL, CtauS, &CtauS, NULL); CHKERRQ(ierr);
  ierr = PetscOptionsScalar("-strong_form",
                            "Strong (1) or weak/integrated by parts (0) advection residual",
                            NULL, strong_form, &strong_form, NULL);
  CHKERRQ(ierr);
  ierr = PetscOptionsScalar("-lx", "Length scale in x direction",
                            NULL, lx, &lx, NULL); CHKERRQ(ierr);
  ierr = PetscOptionsScalar("-ly", "Length scale in y direction",
                            NULL, ly, &ly, NULL); CHKERRQ(ierr);
  ierr = PetscOptionsScalar("-lz", "Length scale in z direction",
                            NULL, lz, &lz, NULL); CHKERRQ(ierr);
  ierr = PetscOptionsScalar("-rc", "Characteristic radius of thermal bubble",
                            NULL, rc, &rc, NULL); CHKERRQ(ierr);
  ierr = PetscOptionsScalar("-resx","Target resolution in x",
                            NULL, resx, &resx, NULL); CHKERRQ(ierr);
  ierr = PetscOptionsScalar("-resy","Target resolution in y",
                            NULL, resy, &resy, NULL); CHKERRQ(ierr);
  ierr = PetscOptionsScalar("-resz","Target resolution in z",
                            NULL, resz, &resz, NULL); CHKERRQ(ierr);
  PetscInt n = problem->dim;
  ierr = PetscOptionsEnumArray("-periodicity", "Periodicity per direction",
                               NULL, DMBoundaryTypes, (PetscEnum *)periodicity,
                               &n, NULL); CHKERRQ(ierr);
  n = problem->dim;
  center[0] = 0.5 * lx;
  center[1] = 0.5 * ly;
  center[2] = 0.5 * lz;
  ierr = PetscOptionsRealArray("-center", "Location of bubble center",
                               NULL, center, &n, NULL); CHKERRQ(ierr);
  n = problem->dim;
  ierr = PetscOptionsRealArray("-dc_axis",
                               "Axis of density current cylindrical anomaly, or {0,0,0} for spherically symmetric",
                               NULL, dc_axis, &n, NULL); CHKERRQ(ierr);
  {
    PetscReal norm = PetscSqrtReal(PetscSqr(dc_axis[0]) +
                                   PetscSqr(dc_axis[1]) + PetscSqr(dc_axis[2]));
    if (norm > 0) {
      for (int i=0; i<3; i++) dc_axis[i] /= norm;
    }
  }
  ierr = PetscOptionsInt("-output_freq",
                         "Frequency of output, in number of steps",
                         NULL, outputfreq, &outputfreq, NULL); CHKERRQ(ierr);
  ierr = PetscOptionsInt("-continue", "Continue from previous solution",
                         NULL, contsteps, &contsteps, NULL); CHKERRQ(ierr);
  ierr = PetscOptionsInt("-degree_volume", "Polynomial degree of finite elements for the Volume",
                         NULL, degreeVol, &degreeVol, NULL); CHKERRQ(ierr);
  ierr = PetscOptionsInt("-qextra_volume", "Number of extra quadrature points for the Volume",
                         NULL, qextraVol, &qextraVol, NULL); CHKERRQ(ierr);
  PetscStrncpy(user->outputfolder, ".", 2);
  ierr = PetscOptionsString("-of", "Output folder",
                            NULL, user->outputfolder, user->outputfolder,
                            sizeof(user->outputfolder), NULL); CHKERRQ(ierr);
  ierr = PetscOptionsEnd(); CHKERRQ(ierr);

  // Define derived units
  Pascal = kilogram / (meter * PetscSqr(second));
  JperkgK =  PetscSqr(meter) / (PetscSqr(second) * Kelvin);
  mpersquareds = meter / PetscSqr(second);
  WpermK = kilogram * meter / (pow(second,3) * Kelvin);
  kgpercubicm = kilogram / pow(meter,3);
  kgpersquaredms = kilogram / (PetscSqr(meter) * second);
  Joulepercubicm = kilogram / (meter * PetscSqr(second));

  // Scale variables to desired units
  theta0 *= Kelvin;
  thetaC *= Kelvin;
  P0 *= Pascal;
  N *= (1./second);
  cv *= JperkgK;
  cp *= JperkgK;
  Rd = cp - cv;
  g *= mpersquareds;
  mu *= Pascal * second;
  k *= WpermK;
  lx = fabs(lx) * meter;
  ly = fabs(ly) * meter;
  lz = fabs(lz) * meter;
  rc = fabs(rc) * meter;
  resx = fabs(resx) * meter;
  resy = fabs(resy) * meter;
  resz = fabs(resz) * meter;
  for (int i=0; i<3; i++) center[i] *= meter;

  const CeedInt dim = problem->dim, ncompx = problem->dim,
                qdatasizeVol = problem->qdatasizeVol;
  // Set up the libCEED context
  struct SetupContext_ ctxSetup =  {
    .theta0 = theta0,
    .thetaC = thetaC,
    .P0 = P0,
    .N = N,
    .cv = cv,
    .cp = cp,
    .Rd = Rd,
    .g = g,
    .rc = rc,
    .lx = lx,
    .ly = ly,
    .lz = lz,
    .periodicity0 = periodicity[0],
    .periodicity1 = periodicity[1],
    .periodicity2 = periodicity[2],
    .center[0] = center[0],
    .center[1] = center[1],
    .center[2] = center[2],
    .dc_axis[0] = dc_axis[0],
    .dc_axis[1] = dc_axis[1],
    .dc_axis[2] = dc_axis[2],
    .time = 0,
  };

  {
    const PetscReal scale[3] = {lx, ly, lz};
    ierr = DMPlexCreateBoxMesh(comm, dim, PETSC_FALSE, NULL, NULL, scale,
                               periodicity, PETSC_TRUE, &dm);
    CHKERRQ(ierr);
  }
  if (1) {
    DM               dmDist = NULL;
    PetscPartitioner part;

    ierr = DMPlexGetPartitioner(dm, &part); CHKERRQ(ierr);
    ierr = PetscPartitionerSetFromOptions(part); CHKERRQ(ierr);
    ierr = DMPlexDistribute(dm, 0, NULL, &dmDist); CHKERRQ(ierr);
    if (dmDist) {
      ierr = DMDestroy(&dm); CHKERRQ(ierr);
      dm  = dmDist;
    }
  }
  ierr = DMViewFromOptions(dm, NULL, "-dm_view"); CHKERRQ(ierr);

  ierr = DMLocalizeCoordinates(dm); CHKERRQ(ierr);
  ierr = DMSetFromOptions(dm); CHKERRQ(ierr);
  ierr = SetUpDM(dm, problem, degreeVol, &bc, &ctxSetup); CHKERRQ(ierr);
  if (!test) {
    ierr = PetscPrintf(PETSC_COMM_WORLD,
                       "Degree of Volumetric FEM Space: %D\n",
                       degreeVol); CHKERRQ(ierr);
  }
  dmviz = NULL;
  interpviz = NULL;
  if (viz_refine) {
    DM dmhierarchy[viz_refine+1];

    ierr = DMPlexSetRefinementUniform(dm, PETSC_TRUE); CHKERRQ(ierr);
    dmhierarchy[0] = dm;
    for (PetscInt i = 0, d = degreeVol; i < viz_refine; i++) {
      Mat interp_next;

      ierr = DMRefine(dmhierarchy[i], MPI_COMM_NULL, &dmhierarchy[i+1]);
      CHKERRQ(ierr);
      ierr = DMSetCoarseDM(dmhierarchy[i+1], dmhierarchy[i]); CHKERRQ(ierr);
      d = (d + 1) / 2;
      if (i + 1 == viz_refine) d = 1;
      ierr = SetUpDM(dmhierarchy[i+1], problem, d, &bc, &ctxSetup); CHKERRQ(ierr);
      ierr = DMCreateInterpolation(dmhierarchy[i], dmhierarchy[i+1],
                                   &interp_next, NULL); CHKERRQ(ierr);
      if (!i) interpviz = interp_next;
      else {
        Mat C;
        ierr = MatMatMult(interp_next, interpviz, MAT_INITIAL_MATRIX,
                          PETSC_DECIDE, &C); CHKERRQ(ierr);
        ierr = MatDestroy(&interp_next); CHKERRQ(ierr);
        ierr = MatDestroy(&interpviz); CHKERRQ(ierr);
        interpviz = C;
      }
    }
    for (PetscInt i=1; i<viz_refine; i++) {
      ierr = DMDestroy(&dmhierarchy[i]); CHKERRQ(ierr);
    }
    dmviz = dmhierarchy[viz_refine];
  }
  ierr = DMCreateGlobalVector(dm, &Q); CHKERRQ(ierr);
  ierr = DMGetLocalVector(dm, &Qloc); CHKERRQ(ierr);
  ierr = VecGetSize(Qloc, &lnodes); CHKERRQ(ierr);
  lnodes /= ncompq;

  {
    // Print grid information
    CeedInt gdofs, odofs;
    int comm_size;
    char box_faces_str[PETSC_MAX_PATH_LEN] = "NONE";
    ierr = VecGetSize(Q, &gdofs); CHKERRQ(ierr);
    ierr = VecGetLocalSize(Q, &odofs); CHKERRQ(ierr);
    ierr = MPI_Comm_size(comm, &comm_size); CHKERRQ(ierr);
    ierr = PetscOptionsGetString(NULL, NULL, "-dm_plex_box_faces", box_faces_str,
                                 sizeof(box_faces_str), NULL); CHKERRQ(ierr);
    if (!test) {
      ierr = PetscPrintf(comm, "Global FEM dofs: %D (%D owned) on %d ranks\n",
                         gdofs, odofs, comm_size); CHKERRQ(ierr);
      ierr = PetscPrintf(comm, "Local FEM nodes: %D\n", lnodes); CHKERRQ(ierr);
      ierr = PetscPrintf(comm, "dm_plex_box_faces: %s\n", box_faces_str);
      CHKERRQ(ierr);
    }

  }

  // Set up global mass vector
  ierr = VecDuplicate(Q,&user->M); CHKERRQ(ierr);

  // Set up CEED
  // CEED Bases
  CeedInit(ceedresource, &ceed);
  numP_Vol = degreeVol + 1;
  numQ_Vol = numP_Vol + qextraVol;
  CeedBasisCreateTensorH1Lagrange(ceed, dim, ncompq, numP_Vol, numQ_Vol, CEED_GAUSS,
                                  &basisqVol);
  CeedBasisCreateTensorH1Lagrange(ceed, dim, ncompx, 2, numQ_Vol, CEED_GAUSS,
                                  &basisxVol);
  CeedBasisCreateTensorH1Lagrange(ceed, dim, ncompx, 2, numP_Vol,
                                  CEED_GAUSS_LOBATTO, &basisxcVol);
  ierr = DMGetCoordinateDM(dm, &dmcoord); CHKERRQ(ierr);
  ierr = DMPlexSetClosurePermutationTensor(dmcoord, PETSC_DETERMINE, NULL);
  CHKERRQ(ierr);

  // CEED Restrictions
  // Restrictions on the Volume
  ierr = GetRestrictionForDomain(ceed, dm, ncompx, dim, 0, 0, 0, numP_Vol, numQ_Vol,
                                 qdatasizeVol, &restrictqVol, &restrictxVol,
                                 &restrictqdiVol); CHKERRQ(ierr);

  ierr = DMGetCoordinatesLocal(dm, &Xloc); CHKERRQ(ierr);
  ierr = CreateVectorFromPetscVec(ceed, Xloc, &xcorners); CHKERRQ(ierr);

  // Create the CEED vectors that will be needed in setup
  CeedInt NqptsVol;
  CeedBasisGetNumQuadraturePoints(basisqVol, &NqptsVol);
  CeedElemRestrictionGetNumElements(restrictqVol, &localNelemVol);
  CeedVectorCreate(ceed, qdatasizeVol*localNelemVol*NqptsVol, &qdataVol);
  CeedElemRestrictionCreateVector(restrictqVol, &q0ceedVol, NULL);

  // Create the Q-function that builds the quadrature data for the NS operator
  CeedQFunctionCreateInterior(ceed, 1, problem->setupVol, problem->setupVol_loc,
                              &qf_setupVol);
  CeedQFunctionAddInput(qf_setupVol, "dx", ncompx*dim, CEED_EVAL_GRAD);
  CeedQFunctionAddInput(qf_setupVol, "weight", 1, CEED_EVAL_WEIGHT);
  CeedQFunctionAddOutput(qf_setupVol, "qdataVol", qdatasizeVol, CEED_EVAL_NONE);

  // Create the Q-function that sets the ICs of the operator
  CeedQFunctionCreateInterior(ceed, 1, problem->ics, problem->ics_loc, &qf_ics);
  CeedQFunctionAddInput(qf_ics, "x", ncompx, CEED_EVAL_INTERP);
  CeedQFunctionAddOutput(qf_ics, "q0", ncompq, CEED_EVAL_NONE);

  qf_rhsVol = NULL;
  if (problem->applyVol_rhs) { // Create the Q-function that defines the action of the RHS operator
    CeedQFunctionCreateInterior(ceed, 1, problem->applyVol_rhs,
                                problem->applyVol_rhs_loc, &qf_rhsVol);
    CeedQFunctionAddInput(qf_rhsVol, "q", ncompq, CEED_EVAL_INTERP);
    CeedQFunctionAddInput(qf_rhsVol, "dq", ncompq*dim, CEED_EVAL_GRAD);
    CeedQFunctionAddInput(qf_rhsVol, "qdataVol", qdatasizeVol, CEED_EVAL_NONE);
    CeedQFunctionAddInput(qf_rhsVol, "x", ncompx, CEED_EVAL_INTERP);
    CeedQFunctionAddOutput(qf_rhsVol, "v", ncompq, CEED_EVAL_INTERP);
    CeedQFunctionAddOutput(qf_rhsVol, "dv", ncompq*dim, CEED_EVAL_GRAD);
  }

  qf_ifunctionVol = NULL;
  if (problem->applyVol_ifunction) { // Create the Q-function that defines the action of the IFunction
    CeedQFunctionCreateInterior(ceed, 1, problem->applyVol_ifunction,
                                problem->applyVol_ifunction_loc, &qf_ifunctionVol);
    CeedQFunctionAddInput(qf_ifunctionVol, "q", ncompq, CEED_EVAL_INTERP);
    CeedQFunctionAddInput(qf_ifunctionVol, "dq", ncompq*dim, CEED_EVAL_GRAD);
    CeedQFunctionAddInput(qf_ifunctionVol, "qdot", ncompq, CEED_EVAL_INTERP);
    CeedQFunctionAddInput(qf_ifunctionVol, "qdataVol", qdatasizeVol, CEED_EVAL_NONE);
    CeedQFunctionAddInput(qf_ifunctionVol, "x", ncompx, CEED_EVAL_INTERP);
    CeedQFunctionAddOutput(qf_ifunctionVol, "v", ncompq, CEED_EVAL_INTERP);
    CeedQFunctionAddOutput(qf_ifunctionVol, "dv", ncompq*dim, CEED_EVAL_GRAD);
  }

  // Create the operator that builds the quadrature data for the NS operator
  CeedOperatorCreate(ceed, qf_setupVol, NULL, NULL, &op_setupVol);
  CeedOperatorSetField(op_setupVol, "dx", restrictxVol, basisxVol, CEED_VECTOR_ACTIVE);
  CeedOperatorSetField(op_setupVol, "weight", CEED_ELEMRESTRICTION_NONE,
                       basisxVol, CEED_VECTOR_NONE);
  CeedOperatorSetField(op_setupVol, "qdataVol", restrictqdiVol,
                       CEED_BASIS_COLLOCATED, CEED_VECTOR_ACTIVE);

  // Create the operator that sets the ICs
  CeedOperatorCreate(ceed, qf_ics, NULL, NULL, &op_ics);
  CeedOperatorSetField(op_ics, "x", restrictxVol, basisxcVol, CEED_VECTOR_ACTIVE);
  CeedOperatorSetField(op_ics, "q0", restrictqVol,
                       CEED_BASIS_COLLOCATED, CEED_VECTOR_ACTIVE);

  CeedElemRestrictionCreateVector(restrictqVol, &user->qceed, NULL);
  CeedElemRestrictionCreateVector(restrictqVol, &user->qdotceed, NULL);
  CeedElemRestrictionCreateVector(restrictqVol, &user->gceed, NULL);

  if (qf_rhsVol) { // Create the RHS physics operator
    CeedOperator op;
    CeedOperatorCreate(ceed, qf_rhsVol, NULL, NULL, &op);
    CeedOperatorSetField(op, "q", restrictqVol, basisqVol, CEED_VECTOR_ACTIVE);
    CeedOperatorSetField(op, "dq", restrictqVol, basisqVol, CEED_VECTOR_ACTIVE);
    CeedOperatorSetField(op, "qdataVol", restrictqdiVol,
                         CEED_BASIS_COLLOCATED, qdataVol);
    CeedOperatorSetField(op, "x", restrictxVol, basisxVol, xcorners);
    CeedOperatorSetField(op, "v", restrictqVol, basisqVol, CEED_VECTOR_ACTIVE);
    CeedOperatorSetField(op, "dv", restrictqVol, basisqVol, CEED_VECTOR_ACTIVE);
    user->op_rhs = op;
  }

  if (qf_ifunctionVol) { // Create the IFunction operator
    CeedOperator op;
    CeedOperatorCreate(ceed, qf_ifunctionVol, NULL, NULL, &op);
    CeedOperatorSetField(op, "q", restrictqVol, basisqVol, CEED_VECTOR_ACTIVE);
    CeedOperatorSetField(op, "dq", restrictqVol, basisqVol, CEED_VECTOR_ACTIVE);
    CeedOperatorSetField(op, "qdot", restrictqVol, basisqVol, user->qdotceed);
    CeedOperatorSetField(op, "qdataVol", restrictqdiVol,
                         CEED_BASIS_COLLOCATED, qdataVol);
    CeedOperatorSetField(op, "x", restrictxVol, basisxVol, xcorners);
    CeedOperatorSetField(op, "v", restrictqVol, basisqVol, CEED_VECTOR_ACTIVE);
    CeedOperatorSetField(op, "dv", restrictqVol, basisqVol, CEED_VECTOR_ACTIVE);
    user->op_ifunction = op;
  }

  //**************************************************************************************//
  // Add boundary Integral (TODO: create a function for all faces)
  //--------------------------------------------------------------------------------------//
  // Set up CEED for the boundaries
  // CEED bases
  CeedInt height = 1;
  CeedInt dimSur = dim - height;
  numP_Sur = degreeSur + 1;
  numQ_Sur = numP_Sur + qextraSur;
  CeedBasisCreateTensorH1Lagrange(ceed, dimSur, ncompq, numP_Sur, numQ_Sur, CEED_GAUSS,
                                  &basisqSur);
  CeedBasisCreateTensorH1Lagrange(ceed, dimSur, ncompx, 2, numQ_Sur, CEED_GAUSS,
                                  &basisxSur);
  CeedBasisCreateTensorH1Lagrange(ceed, dimSur, ncompx, 2, numP_Sur,
                                  CEED_GAUSS_LOBATTO, &basisxcSur);
  // CEED Restrictions
  // Restriction on one face
  DMLabel domainLabel;
  CeedInt qdatasizeSur = 1;
  ierr = DMGetLabel(dm, "Face Sets", &domainLabel); CHKERRQ(ierr);
  ierr = GetRestrictionForDomain(ceed, dm, ncompx, dimSur, height, domainLabel, 2, numP_Sur,
                                 numQ_Sur, qdatasizeSur, &restrictqSur, &restrictxSur,
                                 &restrictqdiSur); CHKERRQ(ierr);

  // Create the CEED vectors that will be needed in setup
  CeedInt NqptsSur;
  CeedBasisGetNumQuadraturePoints(basisqSur, &NqptsSur);
  CeedElemRestrictionGetNumElements(restrictqSur, &localNelemSur);
  CeedVectorCreate(ceed, qdatasizeSur*localNelemSur*NqptsSur, &qdataSur);

  // Create the Q-function that builds the quadrature data for the NS operator
  CeedQFunctionCreateInterior(ceed, 1, problem->setupSur, problem->setupSur_loc,
                              &qf_setupSur);
  CeedQFunctionAddInput(qf_setupSur, "dx", ncompx*dimSur, CEED_EVAL_GRAD);
  CeedQFunctionAddInput(qf_setupSur, "weight", 1, CEED_EVAL_WEIGHT);
  CeedQFunctionAddOutput(qf_setupSur, "qdataSur", qdatasizeSur, CEED_EVAL_NONE);


  qf_rhsSur = NULL;
  if (problem->applySur_rhs) { // Create the Q-function that defines the action of the RHS operator
    CeedQFunctionCreateInterior(ceed, 1, problem->applySur_rhs,
                                problem->applySur_rhs_loc, &qf_rhsSur);
    CeedQFunctionAddInput(qf_rhsSur, "q", ncompq, CEED_EVAL_INTERP);
    CeedQFunctionAddInput(qf_rhsSur, "dq", ncompq*dimSur, CEED_EVAL_GRAD);
    CeedQFunctionAddInput(qf_rhsSur, "qdataSur", qdatasizeSur, CEED_EVAL_NONE);
    CeedQFunctionAddInput(qf_rhsSur, "x", ncompx, CEED_EVAL_INTERP);
    CeedQFunctionAddOutput(qf_rhsSur, "v", ncompq, CEED_EVAL_INTERP);
  }

  qf_ifunctionSur = NULL;
  if (problem->applySur_ifunction) { // Create the Q-function that defines the action of the IFunction
    CeedQFunctionCreateInterior(ceed, 1, problem->applySur_ifunction,
                                problem->applySur_ifunction_loc, &qf_ifunctionSur);
    CeedQFunctionAddInput(qf_ifunctionSur, "q", ncompq, CEED_EVAL_INTERP);
    CeedQFunctionAddInput(qf_ifunctionSur, "dq", ncompq*dimSur, CEED_EVAL_GRAD);
    CeedQFunctionAddInput(qf_ifunctionSur, "qdataSur", qdatasizeSur, CEED_EVAL_NONE);
    CeedQFunctionAddInput(qf_ifunctionSur, "x", ncompx, CEED_EVAL_INTERP);
    CeedQFunctionAddOutput(qf_ifunctionSur, "v", ncompq, CEED_EVAL_INTERP);
  }

  // Create the operator that builds the quadrature data for the NS operator
  CeedOperatorCreate(ceed, qf_setupSur, NULL, NULL, &op_setupSur);
  CeedOperatorSetField(op_setupSur, "dx", restrictxSur, basisxSur, CEED_VECTOR_ACTIVE);
  CeedOperatorSetField(op_setupSur, "weight", CEED_ELEMRESTRICTION_NONE,
                       basisxSur, CEED_VECTOR_NONE);
  CeedOperatorSetField(op_setupSur, "qdataSur", restrictqdiSur,
                       CEED_BASIS_COLLOCATED, CEED_VECTOR_ACTIVE);


  if (qf_rhsSur) { // Create the RHS physics operator
    CeedOperator op;
    CeedOperatorCreate(ceed, qf_rhsSur, NULL, NULL, &op);
    CeedOperatorSetField(op, "q", restrictqSur, basisqSur, CEED_VECTOR_ACTIVE);
    CeedOperatorSetField(op, "dq", restrictqSur, basisqSur, CEED_VECTOR_ACTIVE);
    CeedOperatorSetField(op, "qdataSur", restrictqdiSur,
                         CEED_BASIS_COLLOCATED, qdataSur);
    CeedOperatorSetField(op, "x", restrictxSur, basisxSur, xcorners);
    CeedOperatorSetField(op, "v", restrictqSur, basisqSur, CEED_VECTOR_ACTIVE);
    user->op_rhs_sur = op;
  }

  if (qf_ifunctionSur) { // Create the IFunction operator
    CeedOperator op;
    CeedOperatorCreate(ceed, qf_ifunctionSur, NULL, NULL, &op);
    CeedOperatorSetField(op, "q", restrictqSur, basisqSur, CEED_VECTOR_ACTIVE);
    CeedOperatorSetField(op, "dq", restrictqSur, basisqSur, CEED_VECTOR_ACTIVE);
    CeedOperatorSetField(op, "qdataSur", restrictqdiSur,
                         CEED_BASIS_COLLOCATED, qdataSur);
    CeedOperatorSetField(op, "x", restrictxSur, basisxSur, xcorners);
    CeedOperatorSetField(op, "v", restrictqSur, basisqSur, CEED_VECTOR_ACTIVE);
    user->op_ifunction_sur = op;
  }
  // Composite Operaters
  if (user->op_ifunction_vol) {
    if (user->op_ifunction_sur) {
      // Composite Operators for the IFunction
      CeedCompositeOperatorCreate(ceed, &user->op_ifunction);
      CeedCompositeOperatorAddSub(user->op_ifunction, user->op_ifunction_vol);
      CeedCompositeOperatorAddSub(user->op_ifunction, user->op_ifunction_sur);
  } else {
    user->op_ifunction = user->op_ifunction_vol;
    }
  }
  if (user->op_rhs_vol) {
    if (user->op_rhs_sur) {
      // Composite Operators for the RHS
      CeedCompositeOperatorCreate(ceed, &user->op_rhs);
      CeedCompositeOperatorAddSub(user->op_rhs, user->op_rhs_vol);
      CeedCompositeOperatorAddSub(user->op_rhs, user->op_rhs_sur);
  } else {
    user->op_rhs = user->op_rhs_vol;
    }
  }
  //**************************************************************************************//
  CeedQFunctionSetContext(qf_ics, &ctxSetup, sizeof ctxSetup);
  CeedScalar ctxNS[8] = {lambda, mu, k, cv, cp, g, Rd};
  struct Advection2dContext_ ctxAdvection2d = {
    .CtauS = CtauS,
    .strong_form = strong_form,
    .stabilization = stab,
  };
  switch (problemChoice) {
  case NS_DENSITY_CURRENT:
    if (qf_rhsVol) CeedQFunctionSetContext(qf_rhsVol, &ctxNS, sizeof ctxNS);
    if (qf_ifunctionVol) CeedQFunctionSetContext(qf_ifunctionVol, &ctxNS,
          sizeof ctxNS);
    if (qf_rhsSur) CeedQFunctionSetContext(qf_rhsSur, &ctxNS, sizeof ctxNS);
    if (qf_ifunctionSur) CeedQFunctionSetContext(qf_ifunctionSur, &ctxNS,
          sizeof ctxNS);
    break;
  case NS_ADVECTION:
  case NS_ADVECTION2D:
    if (qf_rhsVol) CeedQFunctionSetContext(qf_rhsVol, &ctxAdvection2d,
                                          sizeof ctxAdvection2d);
    if (qf_ifunctionVol) CeedQFunctionSetContext(qf_ifunctionVol, &ctxAdvection2d,
          sizeof ctxAdvection2d);
    if (qf_rhsSur) CeedQFunctionSetContext(qf_rhsSur, &ctxAdvection2d,
                                          sizeof ctxAdvection2d);
    if (qf_ifunctionSur) CeedQFunctionSetContext(qf_ifunctionSur, &ctxAdvection2d,
          sizeof ctxAdvection2d);
  }

  // Set up PETSc context
  // Set up units structure
  units->meter = meter;
  units->kilogram = kilogram;
  units->second = second;
  units->Kelvin = Kelvin;
  units->Pascal = Pascal;
  units->JperkgK = JperkgK;
  units->mpersquareds = mpersquareds;
  units->WpermK = WpermK;
  units->kgpercubicm = kgpercubicm;
  units->kgpersquaredms = kgpersquaredms;
  units->Joulepercubicm = Joulepercubicm;

  // Set up user structure
  user->comm = comm;
  user->outputfreq = outputfreq;
  user->contsteps = contsteps;
  user->units = units;
  user->dm = dm;
  user->dmviz = dmviz;
  user->interpviz = interpviz;
  user->ceed = ceed;

  // Calculate qdataVol and ICs
  // Set up state global and local vectors
  ierr = VecZeroEntries(Q); CHKERRQ(ierr);

  ierr = VectorPlacePetscVec(q0ceedVol, Qloc); CHKERRQ(ierr);

  // Apply Setup Ceed Operators
  ierr = VectorPlacePetscVec(xcorners, Xloc); CHKERRQ(ierr);
  CeedOperatorApply(op_setupVol, xcorners, qdataVol, CEED_REQUEST_IMMEDIATE);
  ierr = ComputeLumpedMassMatrix(ceed, dm, restrictqVol, basisqVol, restrictqdiVol, qdataVol,
                                 user->M); CHKERRQ(ierr);

  ierr = ICs_PetscMultiplicity(op_ics, xcorners, q0ceedVol, dm, Qloc, Q, restrictqVol,
                               &ctxSetup, 0.0);
  if (1) { // Record boundary values from initial condition and override DMPlexInsertBoundaryValues()
    // We use this for the main simulation DM because the reference DMPlexInsertBoundaryValues() is very slow.  If we
    // disable this, we should still get the same results due to the problem->bc function, but with potentially much
    // slower execution.
    Vec Qbc;
    ierr = DMGetNamedLocalVector(dm, "Qbc", &Qbc); CHKERRQ(ierr);
    ierr = VecCopy(Qloc, Qbc); CHKERRQ(ierr);
    ierr = VecZeroEntries(Qloc); CHKERRQ(ierr);
    ierr = DMGlobalToLocal(dm, Q, INSERT_VALUES, Qloc); CHKERRQ(ierr);
    ierr = VecAXPY(Qbc, -1., Qloc); CHKERRQ(ierr);
    ierr = DMRestoreNamedLocalVector(dm, "Qbc", &Qbc); CHKERRQ(ierr);
    ierr = PetscObjectComposeFunction((PetscObject)dm,
                                      "DMPlexInsertBoundaryValues_C",DMPlexInsertBoundaryValues_NS); CHKERRQ(ierr);
  }

  MPI_Comm_rank(comm, &rank);
  if (!rank) {ierr = PetscMkdir(user->outputfolder); CHKERRQ(ierr);}
  // Gather initial Q values
  // In case of continuation of simulation, set up initial values from binary file
  if (contsteps) { // continue from existent solution
    PetscViewer viewer;
    char filepath[PETSC_MAX_PATH_LEN];
    // Read input
    ierr = PetscSNPrintf(filepath, sizeof filepath, "%s/ns-solution.bin",
                         user->outputfolder);
    CHKERRQ(ierr);
    ierr = PetscViewerBinaryOpen(comm, filepath, FILE_MODE_READ, &viewer);
    CHKERRQ(ierr);
    ierr = VecLoad(Q, viewer); CHKERRQ(ierr);
    ierr = PetscViewerDestroy(&viewer); CHKERRQ(ierr);
  } else {
    //ierr = DMLocalToGlobal(dm, Qloc, INSERT_VALUES, Q);CHKERRQ(ierr);
  }
  ierr = DMRestoreLocalVector(dm, &Qloc); CHKERRQ(ierr);

  // Create and setup TS
  ierr = TSCreate(comm, &ts); CHKERRQ(ierr);
  ierr = TSSetDM(ts, dm); CHKERRQ(ierr);
  if (implicit) {
    ierr = TSSetType(ts, TSBDF); CHKERRQ(ierr);
    if (user->op_ifunction) {
      ierr = TSSetIFunction(ts, NULL, IFunction_NS, &user); CHKERRQ(ierr);
    } else {                    // Implicit integrators can fall back to using an RHSFunction
      ierr = TSSetRHSFunction(ts, NULL, RHS_NS, &user); CHKERRQ(ierr);
    }
  } else {
    if (!user->op_rhs) SETERRQ(comm,PETSC_ERR_ARG_NULL,
                                 "Problem does not provide RHSFunction");
    ierr = TSSetType(ts, TSRK); CHKERRQ(ierr);
    ierr = TSRKSetType(ts, TSRK5F); CHKERRQ(ierr);
    ierr = TSSetRHSFunction(ts, NULL, RHS_NS, &user); CHKERRQ(ierr);
  }
  ierr = TSSetMaxTime(ts, 500. * units->second); CHKERRQ(ierr);
  ierr = TSSetExactFinalTime(ts, TS_EXACTFINALTIME_STEPOVER); CHKERRQ(ierr);
  ierr = TSSetTimeStep(ts, 1.e-2 * units->second); CHKERRQ(ierr);
  if (test) {ierr = TSSetMaxSteps(ts, 1); CHKERRQ(ierr);}
  ierr = TSGetAdapt(ts, &adapt); CHKERRQ(ierr);
  ierr = TSAdaptSetStepLimits(adapt,
                              1.e-12 * units->second,
                              1.e2 * units->second); CHKERRQ(ierr);
  ierr = TSSetFromOptions(ts); CHKERRQ(ierr);
  if (!contsteps) { // print initial condition
    if (!test) {
      ierr = TSMonitor_NS(ts, 0, 0., Q, user); CHKERRQ(ierr);
    }
  } else { // continue from time of last output
    PetscReal time;
    PetscInt count;
    PetscViewer viewer;
    char filepath[PETSC_MAX_PATH_LEN];
    ierr = PetscSNPrintf(filepath, sizeof filepath, "%s/ns-time.bin",
                         user->outputfolder); CHKERRQ(ierr);
    ierr = PetscViewerBinaryOpen(comm, filepath, FILE_MODE_READ, &viewer);
    CHKERRQ(ierr);
    ierr = PetscViewerBinaryRead(viewer, &time, 1, &count, PETSC_REAL);
    CHKERRQ(ierr);
    ierr = PetscViewerDestroy(&viewer); CHKERRQ(ierr);
    ierr = TSSetTime(ts, time * user->units->second); CHKERRQ(ierr);
  }
  if (!test) {
    ierr = TSMonitorSet(ts, TSMonitor_NS, user, NULL); CHKERRQ(ierr);
  }

  // Solve
  start = MPI_Wtime();
  ierr = PetscBarrier((PetscObject)ts); CHKERRQ(ierr);
  ierr = TSSolve(ts, Q); CHKERRQ(ierr);
  cpu_time_used = MPI_Wtime() - start;
  ierr = TSGetSolveTime(ts,&ftime); CHKERRQ(ierr);
  ierr = MPI_Allreduce(MPI_IN_PLACE, &cpu_time_used, 1, MPI_DOUBLE, MPI_MIN,
                       comm); CHKERRQ(ierr);
  if (!test) {
    ierr = PetscPrintf(PETSC_COMM_WORLD,
                       "Time taken for solution: %g\n",
                       (double)cpu_time_used); CHKERRQ(ierr);
  }

  // Get error
  if (problem->non_zero_time && !test) {
    Vec Qexact, Qexactloc;
    PetscReal norm;
    ierr = DMCreateGlobalVector(dm, &Qexact); CHKERRQ(ierr);
    ierr = DMGetLocalVector(dm, &Qexactloc); CHKERRQ(ierr);
    ierr = VecGetSize(Qexactloc, &lnodes); CHKERRQ(ierr);

    ierr = ICs_PetscMultiplicity(op_ics, xcorners, q0ceedVol, dm, Qexactloc, Qexact,
                                 restrictqVol, &ctxSetup, ftime); CHKERRQ(ierr);

    ierr = VecAXPY(Q, -1.0, Qexact);  CHKERRQ(ierr);
    ierr = VecNorm(Q, NORM_MAX, &norm); CHKERRQ(ierr);
    CeedVectorDestroy(&q0ceedVol);
    ierr = PetscPrintf(PETSC_COMM_WORLD,
                       "Max Error: %g\n",
                       (double)norm); CHKERRQ(ierr);
  }

  // Output Statistics
  ierr = TSGetStepNumber(ts,&steps); CHKERRQ(ierr);
  if (!test) {
    ierr = PetscPrintf(PETSC_COMM_WORLD,
                       "Time integrator took %D time steps to reach final time %g\n",
                       steps,(double)ftime); CHKERRQ(ierr);
  }

  // Clean up libCEED
  CeedVectorDestroy(&qdataVol);
  CeedVectorDestroy(&user->qceed);
  CeedVectorDestroy(&user->qdotceed);
  CeedVectorDestroy(&user->gceed);
  CeedVectorDestroy(&xcorners);
  CeedBasisDestroy(&basisqVol);
  CeedBasisDestroy(&basisxVol);
  CeedBasisDestroy(&basisxcVol);
  CeedElemRestrictionDestroy(&restrictqVol);
  CeedElemRestrictionDestroy(&restrictxVol);
  CeedElemRestrictionDestroy(&restrictqdiVol);
  CeedQFunctionDestroy(&qf_setupVol);
  CeedQFunctionDestroy(&qf_ics);
  CeedQFunctionDestroy(&qf_rhsVol);
  CeedQFunctionDestroy(&qf_ifunctionVol);
  CeedOperatorDestroy(&op_setupVol);
  CeedOperatorDestroy(&op_ics);
  CeedOperatorDestroy(&user->op_rhs_vol);
  CeedOperatorDestroy(&user->op_ifunction_vol);
  CeedDestroy(&ceed);

  CeedVectorDestroy(&qdataSur);
  CeedBasisDestroy(&basisqSur);
  CeedBasisDestroy(&basisxSur);
  CeedBasisDestroy(&basisxcSur);
  CeedElemRestrictionDestroy(&restrictqSur);
  CeedElemRestrictionDestroy(&restrictxSur);
  CeedElemRestrictionDestroy(&restrictqdiSur);
  CeedQFunctionDestroy(&qf_setupSur);
  CeedQFunctionDestroy(&qf_rhsSur);
  CeedQFunctionDestroy(&qf_ifunctionSur);
  CeedOperatorDestroy(&op_setupSur);
  CeedOperatorDestroy(&user->op_rhs_sur);
  CeedOperatorDestroy(&user->op_ifunction_sur);

  CeedOperatorDestroy(&user->op_rhs);
  CeedOperatorDestroy(&user->op_ifunction);

  // Clean up PETSc
  ierr = VecDestroy(&Q); CHKERRQ(ierr);
  ierr = VecDestroy(&user->M); CHKERRQ(ierr);
  ierr = MatDestroy(&interpviz); CHKERRQ(ierr);
  ierr = DMDestroy(&dmviz); CHKERRQ(ierr);
  ierr = TSDestroy(&ts); CHKERRQ(ierr);
  ierr = DMDestroy(&dm); CHKERRQ(ierr);
  ierr = PetscFree(units); CHKERRQ(ierr);
  ierr = PetscFree(user); CHKERRQ(ierr);
  return PetscFinalize();
}