1 2 #include <private/kspimpl.h> 3 4 typedef struct { 5 PetscReal haptol; 6 } KSP_SYMMLQ; 7 8 #undef __FUNCT__ 9 #define __FUNCT__ "KSPSetUp_SYMMLQ" 10 PetscErrorCode KSPSetUp_SYMMLQ(KSP ksp) 11 { 12 PetscErrorCode ierr; 13 14 PetscFunctionBegin; 15 if (ksp->pc_side == PC_RIGHT) SETERRQ(((PetscObject)ksp)->comm,PETSC_ERR_SUP,"No right preconditioning for KSPSYMMLQ"); 16 else if (ksp->pc_side == PC_SYMMETRIC) SETERRQ(((PetscObject)ksp)->comm,PETSC_ERR_SUP,"No symmetric preconditioning for KSPSYMMLQ"); 17 ierr = KSPDefaultGetWork(ksp,9);CHKERRQ(ierr); 18 PetscFunctionReturn(0); 19 } 20 21 #undef __FUNCT__ 22 #define __FUNCT__ "KSPSolve_SYMMLQ" 23 PetscErrorCode KSPSolve_SYMMLQ(KSP ksp) 24 { 25 PetscErrorCode ierr; 26 PetscInt i; 27 PetscScalar alpha,beta,ibeta,betaold,beta1,ceta = 0,ceta_oold = 0.0, ceta_old = 0.0,ceta_bar; 28 PetscScalar c=1.0,cold=1.0,s=0.0,sold=0.0,coold,soold,rho0,rho1,rho2,rho3; 29 PetscScalar dp = 0.0; 30 PetscReal np,s_prod; 31 Vec X,B,R,Z,U,V,W,UOLD,VOLD,Wbar; 32 Mat Amat,Pmat; 33 MatStructure pflag; 34 KSP_SYMMLQ *symmlq = (KSP_SYMMLQ*)ksp->data; 35 PetscBool diagonalscale; 36 37 PetscFunctionBegin; 38 ierr = PCGetDiagonalScale(ksp->pc,&diagonalscale);CHKERRQ(ierr); 39 if (diagonalscale) SETERRQ1(((PetscObject)ksp)->comm,PETSC_ERR_SUP,"Krylov method %s does not support diagonal scaling",((PetscObject)ksp)->type_name); 40 41 X = ksp->vec_sol; 42 B = ksp->vec_rhs; 43 R = ksp->work[0]; 44 Z = ksp->work[1]; 45 U = ksp->work[2]; 46 V = ksp->work[3]; 47 W = ksp->work[4]; 48 UOLD = ksp->work[5]; 49 VOLD = ksp->work[6]; 50 Wbar = ksp->work[7]; 51 52 ierr = PCGetOperators(ksp->pc,&Amat,&Pmat,&pflag);CHKERRQ(ierr); 53 54 ksp->its = 0; 55 56 ierr = VecSet(UOLD,0.0);CHKERRQ(ierr); /* u_old <- zeros; */ 57 ierr = VecCopy(UOLD,VOLD);CHKERRQ(ierr); /* v_old <- u_old; */ 58 ierr = VecCopy(UOLD,W);CHKERRQ(ierr); /* w <- u_old; */ 59 ierr = VecCopy(UOLD,Wbar);CHKERRQ(ierr); /* w_bar <- u_old; */ 60 if (!ksp->guess_zero) { 61 ierr = KSP_MatMult(ksp,Amat,X,R);CHKERRQ(ierr); /* r <- b - A*x */ 62 ierr = VecAYPX(R,-1.0,B);CHKERRQ(ierr); 63 } else { 64 ierr = VecCopy(B,R);CHKERRQ(ierr); /* r <- b (x is 0) */ 65 } 66 67 ierr = KSP_PCApply(ksp,R,Z);CHKERRQ(ierr); /* z <- B*r */ 68 ierr = VecDot(R,Z,&dp);CHKERRQ(ierr); /* dp = r'*z; */ 69 if (PetscAbsScalar(dp) < symmlq->haptol) { 70 ierr = PetscInfo2(ksp,"Detected happy breakdown %G tolerance %G\n",PetscAbsScalar(dp),symmlq->haptol);CHKERRQ(ierr); 71 ksp->rnorm = 0.0; /* what should we really put here? */ 72 ksp->reason = KSP_CONVERGED_HAPPY_BREAKDOWN; /* bugfix proposed by Lourens (lourens.vanzanen@shell.com) */ 73 PetscFunctionReturn(0); 74 } 75 76 #if !defined(PETSC_USE_COMPLEX) 77 if (dp < 0.0) { 78 ksp->reason = KSP_DIVERGED_INDEFINITE_PC; 79 PetscFunctionReturn(0); 80 } 81 #endif 82 dp = PetscSqrtScalar(dp); 83 beta = dp; /* beta <- sqrt(r'*z) */ 84 beta1 = beta; 85 s_prod = PetscAbsScalar(beta1); 86 87 ierr = VecCopy(R,V);CHKERRQ(ierr); /* v <- r; */ 88 ierr = VecCopy(Z,U);CHKERRQ(ierr); /* u <- z; */ 89 ibeta = 1.0 / beta; 90 ierr = VecScale(V,ibeta);CHKERRQ(ierr); /* v <- ibeta*v; */ 91 ierr = VecScale(U,ibeta);CHKERRQ(ierr); /* u <- ibeta*u; */ 92 ierr = VecCopy(U,Wbar);CHKERRQ(ierr); /* w_bar <- u; */ 93 ierr = VecNorm(Z,NORM_2,&np);CHKERRQ(ierr); /* np <- ||z|| */ 94 KSPLogResidualHistory(ksp,np); 95 ierr = KSPMonitor(ksp,0,np);CHKERRQ(ierr); 96 ksp->rnorm = np; 97 ierr = (*ksp->converged)(ksp,0,np,&ksp->reason,ksp->cnvP);CHKERRQ(ierr); /* test for convergence */ 98 if (ksp->reason) PetscFunctionReturn(0); 99 100 i = 0; ceta = 0.; 101 do { 102 ksp->its = i+1; 103 104 /* Update */ 105 if (ksp->its > 1){ 106 ierr = VecCopy(V,VOLD);CHKERRQ(ierr); /* v_old <- v; */ 107 ierr = VecCopy(U,UOLD);CHKERRQ(ierr); /* u_old <- u; */ 108 109 ierr = VecCopy(R,V);CHKERRQ(ierr); 110 ierr = VecScale(V,1.0/beta);CHKERRQ(ierr); /* v <- ibeta*r; */ 111 ierr = VecCopy(Z,U);CHKERRQ(ierr); 112 ierr = VecScale(U,1.0/beta);CHKERRQ(ierr); /* u <- ibeta*z; */ 113 114 ierr = VecCopy(Wbar,W);CHKERRQ(ierr); 115 ierr = VecScale(W,c);CHKERRQ(ierr); 116 ierr = VecAXPY(W,s,U);CHKERRQ(ierr); /* w <- c*w_bar + s*u; (w_k) */ 117 ierr = VecScale(Wbar,-s);CHKERRQ(ierr); 118 ierr = VecAXPY(Wbar,c,U);CHKERRQ(ierr); /* w_bar <- -s*w_bar + c*u; (w_bar_(k+1)) */ 119 ierr = VecAXPY(X,ceta,W);CHKERRQ(ierr); /* x <- x + ceta * w; (xL_k) */ 120 121 ceta_oold = ceta_old; 122 ceta_old = ceta; 123 } 124 125 /* Lanczos */ 126 ierr = KSP_MatMult(ksp,Amat,U,R);CHKERRQ(ierr); /* r <- Amat*u; */ 127 ierr = VecDot(U,R,&alpha);CHKERRQ(ierr); /* alpha <- u'*r; */ 128 ierr = KSP_PCApply(ksp,R,Z);CHKERRQ(ierr); /* z <- B*r; */ 129 130 ierr = VecAXPY(R,-alpha,V);CHKERRQ(ierr); /* r <- r - alpha* v; */ 131 ierr = VecAXPY(Z,-alpha,U);CHKERRQ(ierr); /* z <- z - alpha* u; */ 132 ierr = VecAXPY(R,-beta,VOLD);CHKERRQ(ierr); /* r <- r - beta * v_old; */ 133 ierr = VecAXPY(Z,-beta,UOLD);CHKERRQ(ierr); /* z <- z - beta * u_old; */ 134 betaold = beta; /* beta_k */ 135 ierr = VecDot(R,Z,&dp);CHKERRQ(ierr); /* dp <- r'*z; */ 136 if (PetscAbsScalar(dp) < symmlq->haptol) { 137 ierr = PetscInfo2(ksp,"Detected happy breakdown %G tolerance %G\n",PetscAbsScalar(dp),symmlq->haptol);CHKERRQ(ierr); 138 dp = 0.0; 139 } 140 141 #if !defined(PETSC_USE_COMPLEX) 142 if (dp < 0.0) { 143 ksp->reason = KSP_DIVERGED_INDEFINITE_PC; 144 break; 145 } 146 #endif 147 beta = PetscSqrtScalar(dp); /* beta = sqrt(dp); */ 148 149 /* QR factorization */ 150 coold = cold; cold = c; soold = sold; sold = s; 151 rho0 = cold * alpha - coold * sold * betaold; /* gamma_bar */ 152 rho1 = PetscSqrtScalar(rho0*rho0 + beta*beta); /* gamma */ 153 rho2 = sold * alpha + coold * cold * betaold; /* delta */ 154 rho3 = soold * betaold; /* epsilon */ 155 156 /* Givens rotation: [c -s; s c] (different from the Reference!) */ 157 c = rho0 / rho1; s = beta / rho1; 158 159 if (ksp->its==1){ 160 ceta = beta1/rho1; 161 } else { 162 ceta = -(rho2*ceta_old + rho3*ceta_oold)/rho1; 163 } 164 165 s_prod = s_prod*PetscAbsScalar(s); 166 if (c == 0.0){ 167 np = s_prod*1.e16; 168 } else { 169 np = s_prod/PetscAbsScalar(c); /* residual norm for xc_k (CGNORM) */ 170 } 171 ksp->rnorm = np; 172 KSPLogResidualHistory(ksp,np); 173 ierr = KSPMonitor(ksp,i+1,np);CHKERRQ(ierr); 174 ierr = (*ksp->converged)(ksp,i+1,np,&ksp->reason,ksp->cnvP);CHKERRQ(ierr); /* test for convergence */ 175 if (ksp->reason) break; 176 i++; 177 } while (i<ksp->max_it); 178 179 /* move to the CG point: xc_(k+1) */ 180 if (c == 0.0){ 181 ceta_bar = ceta*1.e15; 182 } else { 183 ceta_bar = ceta/c; 184 } 185 ierr = VecAXPY(X,ceta_bar,Wbar);CHKERRQ(ierr); /* x <- x + ceta_bar*w_bar */ 186 187 if (i >= ksp->max_it) { 188 ksp->reason = KSP_DIVERGED_ITS; 189 } 190 PetscFunctionReturn(0); 191 } 192 193 /*MC 194 KSPSYMMLQ - This code implements the SYMMLQ method. 195 196 Options Database Keys: 197 . see KSPSolve() 198 199 Level: beginner 200 201 Notes: The operator and the preconditioner must be symmetric for this method. The 202 preconditioner must be POSITIVE-DEFINITE. 203 204 Supports only left preconditioning. 205 206 Reference: Paige & Saunders, 1975. 207 208 .seealso: KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP 209 M*/ 210 EXTERN_C_BEGIN 211 #undef __FUNCT__ 212 #define __FUNCT__ "KSPCreate_SYMMLQ" 213 PetscErrorCode KSPCreate_SYMMLQ(KSP ksp) 214 { 215 KSP_SYMMLQ *symmlq; 216 PetscErrorCode ierr; 217 218 PetscFunctionBegin; 219 if (ksp->pc_side != PC_LEFT) { 220 ierr = PetscInfo(ksp,"WARNING! Setting PC_SIDE for SYMMLQ to left!\n");CHKERRQ(ierr); 221 } 222 ksp->pc_side = PC_LEFT; 223 ierr = PetscNewLog(ksp,KSP_SYMMLQ,&symmlq);CHKERRQ(ierr); 224 symmlq->haptol = 1.e-18; 225 ksp->data = (void*)symmlq; 226 227 /* 228 Sets the functions that are associated with this data structure 229 (in C++ this is the same as defining virtual functions) 230 */ 231 ksp->ops->setup = KSPSetUp_SYMMLQ; 232 ksp->ops->solve = KSPSolve_SYMMLQ; 233 ksp->ops->destroy = KSPDefaultDestroy; 234 ksp->ops->setfromoptions = 0; 235 ksp->ops->buildsolution = KSPDefaultBuildSolution; 236 ksp->ops->buildresidual = KSPDefaultBuildResidual; 237 PetscFunctionReturn(0); 238 } 239 EXTERN_C_END 240 241 242 243 244 245