// Copyright (c) 2017-2018, 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.

#include <ceed-impl.h>
#include <string.h>
#include "ceed-ref.h"

// Contracts on the middle index
// NOTRANSPOSE: V_ajc = T_jb U_abc
// TRANSPOSE:   V_ajc = T_bj U_abc
// If Add != 0, "=" is replaced by "+="
static int CeedTensorContract_Ref(Ceed ceed,
                                  CeedInt A, CeedInt B, CeedInt C, CeedInt J,
                                  const CeedScalar *t, CeedTransposeMode tmode,
                                  const CeedInt Add,
                                  const CeedScalar *u, CeedScalar *v) {
  CeedInt tstride0 = B, tstride1 = 1;
  if (tmode == CEED_TRANSPOSE) {
    tstride0 = 1; tstride1 = J;
  }

  for (CeedInt a=0; a<A; a++) {
    for (CeedInt j=0; j<J; j++) {
      if (!Add) {
        for (CeedInt c=0; c<C; c++)
          v[(a*J+j)*C+c] = 0;
      }
      for (CeedInt b=0; b<B; b++) {
        for (CeedInt c=0; c<C; c++) {
          v[(a*J+j)*C+c] += t[j*tstride0 + b*tstride1] * u[(a*B+b)*C+c];
        }
      }
    }
  }
  return 0;
}

static int CeedBasisApply_Ref(CeedBasis basis, CeedTransposeMode tmode,
                              CeedEvalMode emode,
                              const CeedScalar *u, CeedScalar *v) {
  int ierr;
  const CeedInt dim = basis->dim;
  const CeedInt ndof = basis->ndof;
  const CeedInt nqpt = ndof*CeedPowInt(basis->Q1d, dim);
  const CeedInt add = (tmode == CEED_TRANSPOSE);

  if (tmode == CEED_TRANSPOSE) {
    const CeedInt vsize = ndof*CeedPowInt(basis->P1d, dim);
    for (CeedInt i = 0; i < vsize; i++)
      v[i] = (CeedScalar) 0;
  }
  if (emode & CEED_EVAL_INTERP) {
    CeedInt P = basis->P1d, Q = basis->Q1d;
    if (tmode == CEED_TRANSPOSE) {
      P = basis->Q1d; Q = basis->P1d;
    }
    CeedInt pre = ndof*CeedPowInt(P, dim-1), post = 1;
    CeedScalar tmp[2][ndof*Q*CeedPowInt(P>Q?P:Q, dim-1)];
    for (CeedInt d=0; d<dim; d++) {
      ierr = CeedTensorContract_Ref(basis->ceed, pre, P, post, Q, basis->interp1d,
                                    tmode, add&&(d==dim-1),
                                    d==0?u:tmp[d%2], d==dim-1?v:tmp[(d+1)%2]);
      CeedChk(ierr);
      pre /= P;
      post *= Q;
    }
    if (tmode == CEED_NOTRANSPOSE) {
      v += nqpt;
    } else {
      u += nqpt;
    }
  }
  if (emode & CEED_EVAL_GRAD) {
    CeedInt P = basis->P1d, Q = basis->Q1d;
    // In CEED_NOTRANSPOSE mode:
    // u is (P^dim x nc), column-major layout (nc = ndof)
    // v is (Q^dim x nc x dim), column-major layout (nc = ndof)
    // In CEED_TRANSPOSE mode, the sizes of u and v are switched.
    if (tmode == CEED_TRANSPOSE) {
      P = basis->Q1d, Q = basis->P1d;
    }
    CeedScalar tmp[2][ndof*Q*CeedPowInt(P>Q?P:Q, dim-1)];
    for (CeedInt p = 0; p < dim; p++) {
      CeedInt pre = ndof*CeedPowInt(P, dim-1), post = 1;
      for (CeedInt d=0; d<dim; d++) {
        ierr = CeedTensorContract_Ref(basis->ceed, pre, P, post, Q,
                                      (p==d)?basis->grad1d:basis->interp1d,
                                      tmode, add&&(d==dim-1),
                                      d==0?u:tmp[d%2], d==dim-1?v:tmp[(d+1)%2]);
        CeedChk(ierr);
        pre /= P;
        post *= Q;
      }
      if (tmode == CEED_NOTRANSPOSE) {
        v += nqpt;
      } else {
        u += nqpt;
      }
    }
  }
  if (emode & CEED_EVAL_WEIGHT) {
    if (tmode == CEED_TRANSPOSE)
      return CeedError(basis->ceed, 1,
                       "CEED_EVAL_WEIGHT incompatible with CEED_TRANSPOSE");
    CeedInt Q = basis->Q1d;
    for (CeedInt d=0; d<dim; d++) {
      CeedInt pre = CeedPowInt(Q, dim-d-1), post = CeedPowInt(Q, d);
      for (CeedInt i=0; i<pre; i++) {
        for (CeedInt j=0; j<Q; j++) {
          for (CeedInt k=0; k<post; k++) {
            v[(i*Q + j)*post + k] = basis->qweight1d[j]
                                    * (d == 0 ? 1 : v[(i*Q + j)*post + k]);
          }
        }
      }
    }
  }
  return 0;
}

static int CeedBasisDestroy_Ref(CeedBasis basis) {
  return 0;
}

int CeedBasisCreateTensorH1_Ref(Ceed ceed, CeedInt dim, CeedInt P1d,
                                CeedInt Q1d, const CeedScalar *interp1d,
                                const CeedScalar *grad1d,
                                const CeedScalar *qref1d,
                                const CeedScalar *qweight1d,
                                CeedBasis basis) {
  basis->Apply = CeedBasisApply_Ref;
  basis->Destroy = CeedBasisDestroy_Ref;
  return 0;
}