1 2 /* 3 This file implements FBiCGStab-R. 4 Only allow right preconditioning. 5 FBiCGStab-R is a mathematically equivalent variant of FBiCGStab. Differences are: 6 (1) There are fewer MPI_Allreduce calls. 7 (2) The convergence occasionally is much faster than that of FBiCGStab. 8 */ 9 #include <../src/ksp/ksp/impls/bcgs/bcgsimpl.h> /*I "petscksp.h" I*/ 10 #include <petsc/private/vecimpl.h> 11 12 #undef __FUNCT__ 13 #define __FUNCT__ "KSPSetUp_FBCGSR" 14 static PetscErrorCode KSPSetUp_FBCGSR(KSP ksp) 15 { 16 PetscErrorCode ierr; 17 18 PetscFunctionBegin; 19 ierr = KSPSetWorkVecs(ksp,8);CHKERRQ(ierr); 20 PetscFunctionReturn(0); 21 } 22 23 #include <petsc/private/pcimpl.h> /*I "petscksp.h" I*/ 24 #undef __FUNCT__ 25 #define __FUNCT__ "KSPSolve_FBCGSR" 26 static PetscErrorCode KSPSolve_FBCGSR(KSP ksp) 27 { 28 PetscErrorCode ierr; 29 PetscInt i,j,N; 30 PetscScalar tau,sigma,alpha,omega,beta; 31 PetscReal rho; 32 PetscScalar xi1,xi2,xi3,xi4; 33 Vec X,B,P,P2,RP,R,V,S,T,S2; 34 PetscScalar *PETSC_RESTRICT rp, *PETSC_RESTRICT r, *PETSC_RESTRICT p; 35 PetscScalar *PETSC_RESTRICT v, *PETSC_RESTRICT s, *PETSC_RESTRICT t, *PETSC_RESTRICT s2; 36 PetscScalar insums[4],outsums[4]; 37 KSP_BCGS *bcgs = (KSP_BCGS*)ksp->data; 38 PC pc; 39 40 PetscFunctionBegin; 41 if (!ksp->vec_rhs->petscnative) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"Only coded for PETSc vectors"); 42 ierr = VecGetLocalSize(ksp->vec_sol,&N);CHKERRQ(ierr); 43 44 X = ksp->vec_sol; 45 B = ksp->vec_rhs; 46 P2 = ksp->work[0]; 47 48 /* The followings are involved in modified inner product calculations and vector updates */ 49 RP = ksp->work[1]; ierr = VecGetArray(RP,(PetscScalar**)&rp);CHKERRQ(ierr); ierr = VecRestoreArray(RP,NULL);CHKERRQ(ierr); 50 R = ksp->work[2]; ierr = VecGetArray(R,(PetscScalar**)&r);CHKERRQ(ierr); ierr = VecRestoreArray(R,NULL);CHKERRQ(ierr); 51 P = ksp->work[3]; ierr = VecGetArray(P,(PetscScalar**)&p);CHKERRQ(ierr); ierr = VecRestoreArray(P,NULL);CHKERRQ(ierr); 52 V = ksp->work[4]; ierr = VecGetArray(V,(PetscScalar**)&v);CHKERRQ(ierr); ierr = VecRestoreArray(V,NULL);CHKERRQ(ierr); 53 S = ksp->work[5]; ierr = VecGetArray(S,(PetscScalar**)&s);CHKERRQ(ierr); ierr = VecRestoreArray(S,NULL);CHKERRQ(ierr); 54 T = ksp->work[6]; ierr = VecGetArray(T,(PetscScalar**)&t);CHKERRQ(ierr); ierr = VecRestoreArray(T,NULL);CHKERRQ(ierr); 55 S2 = ksp->work[7]; ierr = VecGetArray(S2,(PetscScalar**)&s2);CHKERRQ(ierr); ierr = VecRestoreArray(S2,NULL);CHKERRQ(ierr); 56 57 /* Only supports right preconditioning */ 58 if (ksp->pc_side != PC_RIGHT) SETERRQ1(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"KSP fbcgsr does not support %s",PCSides[ksp->pc_side]); 59 if (!ksp->guess_zero) { 60 if (!bcgs->guess) { 61 ierr = VecDuplicate(X,&bcgs->guess);CHKERRQ(ierr); 62 } 63 ierr = VecCopy(X,bcgs->guess);CHKERRQ(ierr); 64 } else { 65 ierr = VecSet(X,0.0);CHKERRQ(ierr); 66 } 67 68 /* Compute initial residual */ 69 ierr = KSPGetPC(ksp,&pc);CHKERRQ(ierr); 70 ierr = PCSetUp(pc);CHKERRQ(ierr); 71 if (!ksp->guess_zero) { 72 ierr = KSP_MatMult(ksp,pc->mat,X,P2);CHKERRQ(ierr); /* P2 is used as temporary storage */ 73 ierr = VecCopy(B,R);CHKERRQ(ierr); 74 ierr = VecAXPY(R,-1.0,P2);CHKERRQ(ierr); 75 } else { 76 ierr = VecCopy(B,R);CHKERRQ(ierr); 77 } 78 79 /* Test for nothing to do */ 80 ierr = VecNorm(R,NORM_2,&rho);CHKERRQ(ierr); 81 ierr = PetscObjectSAWsTakeAccess((PetscObject)ksp);CHKERRQ(ierr); 82 ksp->its = 0; 83 ksp->rnorm = rho; 84 ierr = PetscObjectSAWsGrantAccess((PetscObject)ksp);CHKERRQ(ierr); 85 ierr = KSPLogResidualHistory(ksp,rho);CHKERRQ(ierr); 86 ierr = KSPMonitor(ksp,0,rho);CHKERRQ(ierr); 87 ierr = (*ksp->converged)(ksp,0,rho,&ksp->reason,ksp->cnvP);CHKERRQ(ierr); 88 if (ksp->reason) PetscFunctionReturn(0); 89 90 /* Initialize iterates */ 91 ierr = VecCopy(R,RP);CHKERRQ(ierr); /* rp <- r */ 92 ierr = VecCopy(R,P);CHKERRQ(ierr); /* p <- r */ 93 94 /* Big loop */ 95 for (i=0; i<ksp->max_it; i++) { 96 97 /* matmult and pc */ 98 ierr = KSP_PCApply(ksp,P,P2);CHKERRQ(ierr); /* p2 <- K p */ 99 ierr = KSP_MatMult(ksp,pc->mat,P2,V);CHKERRQ(ierr); /* v <- A p2 */ 100 101 /* inner prodcuts */ 102 if (i==0) { 103 tau = rho*rho; 104 ierr = VecDot(V,RP,&sigma);CHKERRQ(ierr); /* sigma <- (v,rp) */ 105 } else { 106 ierr = PetscLogEventBegin(VEC_ReduceArithmetic,0,0,0,0);CHKERRQ(ierr); 107 tau = sigma = 0.0; 108 for (j=0; j<N; j++) { 109 tau += r[j]*rp[j]; /* tau <- (r,rp) */ 110 sigma += v[j]*rp[j]; /* sigma <- (v,rp) */ 111 } 112 ierr = PetscLogFlops(4.0*N);CHKERRQ(ierr); 113 ierr = PetscLogEventEnd(VEC_ReduceArithmetic,0,0,0,0);CHKERRQ(ierr); 114 insums[0] = tau; 115 insums[1] = sigma; 116 ierr = PetscLogEventBarrierBegin(VEC_ReduceBarrier,0,0,0,0,PetscObjectComm((PetscObject)ksp));CHKERRQ(ierr); 117 ierr = MPIU_Allreduce(insums,outsums,2,MPIU_SCALAR,MPIU_SUM,PetscObjectComm((PetscObject)ksp));CHKERRQ(ierr); 118 ierr = PetscLogEventBarrierEnd(VEC_ReduceBarrier,0,0,0,0,PetscObjectComm((PetscObject)ksp));CHKERRQ(ierr); 119 tau = outsums[0]; 120 sigma = outsums[1]; 121 } 122 123 /* scalar update */ 124 alpha = tau / sigma; 125 126 /* vector update */ 127 ierr = VecWAXPY(S,-alpha,V,R);CHKERRQ(ierr); /* s <- r - alpha v */ 128 129 /* matmult and pc */ 130 ierr = KSP_PCApply(ksp,S,S2);CHKERRQ(ierr); /* s2 <- K s */ 131 ierr = KSP_MatMult(ksp,pc->mat,S2,T);CHKERRQ(ierr); /* t <- A s2 */ 132 133 /* inner prodcuts */ 134 ierr = PetscLogEventBegin(VEC_ReduceArithmetic,0,0,0,0);CHKERRQ(ierr); 135 xi1 = xi2 = xi3 = xi4 = 0.0; 136 for (j=0; j<N; j++) { 137 xi1 += s[j]*s[j]; /* xi1 <- (s,s) */ 138 xi2 += t[j]*s[j]; /* xi2 <- (t,s) */ 139 xi3 += t[j]*t[j]; /* xi3 <- (t,t) */ 140 xi4 += t[j]*rp[j]; /* xi4 <- (t,rp) */ 141 } 142 ierr = PetscLogFlops(8.0*N);CHKERRQ(ierr); 143 ierr = PetscLogEventEnd(VEC_ReduceArithmetic,0,0,0,0);CHKERRQ(ierr); 144 145 insums[0] = xi1; 146 insums[1] = xi2; 147 insums[2] = xi3; 148 insums[3] = xi4; 149 150 ierr = PetscLogEventBarrierBegin(VEC_ReduceBarrier,0,0,0,0,PetscObjectComm((PetscObject)ksp));CHKERRQ(ierr); 151 ierr = MPIU_Allreduce(insums,outsums,4,MPIU_SCALAR,MPIU_SUM,PetscObjectComm((PetscObject)ksp));CHKERRQ(ierr); 152 ierr = PetscLogEventBarrierEnd(VEC_ReduceBarrier,0,0,0,0,PetscObjectComm((PetscObject)ksp));CHKERRQ(ierr); 153 xi1 = outsums[0]; 154 xi2 = outsums[1]; 155 xi3 = outsums[2]; 156 xi4 = outsums[3]; 157 158 /* test denominator */ 159 if (xi3 == 0.0) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_PLIB,"Divide by zero"); 160 if (sigma == 0.0) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_PLIB,"Divide by zero"); 161 162 /* scalar updates */ 163 omega = xi2 / xi3; 164 beta = -xi4 / sigma; 165 rho = PetscSqrtReal(PetscAbsScalar(xi1 - omega * xi2)); /* residual norm */ 166 167 /* vector updates */ 168 ierr = VecAXPBYPCZ(X,alpha,omega,1.0,P2,S2);CHKERRQ(ierr); /* x <- alpha * p2 + omega * s2 + x */ 169 170 /* convergence test */ 171 ierr = PetscObjectSAWsTakeAccess((PetscObject)ksp);CHKERRQ(ierr); 172 ksp->its++; 173 ksp->rnorm = rho; 174 ierr = PetscObjectSAWsGrantAccess((PetscObject)ksp);CHKERRQ(ierr); 175 ierr = KSPLogResidualHistory(ksp,rho);CHKERRQ(ierr); 176 ierr = KSPMonitor(ksp,i+1,rho);CHKERRQ(ierr); 177 ierr = (*ksp->converged)(ksp,i+1,rho,&ksp->reason,ksp->cnvP);CHKERRQ(ierr); 178 if (ksp->reason) break; 179 180 /* vector updates */ 181 ierr = PetscLogEventBegin(VEC_Ops,0,0,0,0);CHKERRQ(ierr); 182 for (j=0; j<N; j++) { 183 r[j] = s[j] - omega * t[j]; /* r <- s - omega t */ 184 p[j] = r[j] + beta * (p[j] - omega * v[j]); /* p <- r + beta * (p - omega v) */ 185 } 186 ierr = PetscLogFlops(6.0*N);CHKERRQ(ierr); 187 ierr = PetscLogEventEnd(VEC_Ops,0,0,0,0);CHKERRQ(ierr); 188 189 } 190 191 if (i >= ksp->max_it) ksp->reason = KSP_DIVERGED_ITS; 192 PetscFunctionReturn(0); 193 } 194 195 /*MC 196 KSPFBCGSR - Implements a mathematically equivalent variant of FBiCGSTab. 197 198 Options Database Keys: 199 . see KSPSolve() 200 201 Level: beginner 202 203 Notes: Only allow right preconditioning 204 205 .seealso: KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPBICG, KSPFBCGSL, KSPSetPCSide() 206 M*/ 207 #undef __FUNCT__ 208 #define __FUNCT__ "KSPCreate_FBCGSR" 209 PETSC_EXTERN PetscErrorCode KSPCreate_FBCGSR(KSP ksp) 210 { 211 PetscErrorCode ierr; 212 KSP_BCGS *bcgs; 213 214 PetscFunctionBegin; 215 ierr = PetscNewLog(ksp,&bcgs);CHKERRQ(ierr); 216 217 ksp->data = bcgs; 218 ksp->ops->setup = KSPSetUp_FBCGSR; 219 ksp->ops->solve = KSPSolve_FBCGSR; 220 ksp->ops->destroy = KSPDestroy_BCGS; 221 ksp->ops->reset = KSPReset_BCGS; 222 ksp->ops->buildsolution = KSPBuildSolution_BCGS; 223 ksp->ops->buildresidual = KSPBuildResidualDefault; 224 ksp->ops->setfromoptions = KSPSetFromOptions_BCGS; 225 ksp->pc_side = PC_RIGHT; /* set default PC side */ 226 227 ierr = KSPSetSupportedNorm(ksp,KSP_NORM_PRECONDITIONED,PC_LEFT,3);CHKERRQ(ierr); 228 ierr = KSPSetSupportedNorm(ksp,KSP_NORM_UNPRECONDITIONED,PC_RIGHT,2);CHKERRQ(ierr); 229 PetscFunctionReturn(0); 230 } 231