Actual source code: lcd.c

petsc-master 2019-06-18
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  2:  #include <../src/ksp/ksp/impls/lcd/lcdimpl.h>

  4: PetscErrorCode KSPSetUp_LCD(KSP ksp)
  5: {
  6:   KSP_LCD        *lcd = (KSP_LCD*)ksp->data;
  8:   PetscInt       restart = lcd->restart;

 11:   /* get work vectors needed by LCD */
 12:   KSPSetWorkVecs(ksp,2);

 14:   VecDuplicateVecs(ksp->work[0],restart+1,&lcd->P);
 15:   VecDuplicateVecs(ksp->work[0], restart + 1, &lcd->Q);
 16:   PetscLogObjectMemory((PetscObject)ksp,2*(restart+2)*sizeof(Vec));
 17:   return(0);
 18: }

 20: /*     KSPSolve_LCD - This routine actually applies the left conjugate
 21:     direction method

 23:    Input Parameter:
 24: .     ksp - the Krylov space object that was set to use LCD, by, for
 25:             example, KSPCreate(MPI_Comm,KSP *ksp); KSPSetType(ksp,KSPLCD);

 27:    Output Parameter:
 28: .     its - number of iterations used

 30: */
 31: PetscErrorCode  KSPSolve_LCD(KSP ksp)
 32: {
 34:   PetscInt       it,j,max_k;
 35:   PetscScalar    alfa, beta, num, den, mone;
 36:   PetscReal      rnorm;
 37:   Vec            X,B,R,Z;
 38:   KSP_LCD        *lcd;
 39:   Mat            Amat,Pmat;
 40:   PetscBool      diagonalscale;

 43:   PCGetDiagonalScale(ksp->pc,&diagonalscale);
 44:   if (diagonalscale) SETERRQ1(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"Krylov method %s does not support diagonal scaling",((PetscObject)ksp)->type_name);

 46:   lcd   = (KSP_LCD*)ksp->data;
 47:   X     = ksp->vec_sol;
 48:   B     = ksp->vec_rhs;
 49:   R     = ksp->work[0];
 50:   Z     = ksp->work[1];
 51:   max_k = lcd->restart;
 52:   mone  = -1;

 54:   PCGetOperators(ksp->pc,&Amat,&Pmat);

 56:   ksp->its = 0;
 57:   if (!ksp->guess_zero) {
 58:     KSP_MatMult(ksp,Amat,X,Z);             /*   z <- b - Ax       */
 59:     VecAYPX(Z,mone,B);
 60:   } else {
 61:     VecCopy(B,Z);                         /*     z <- b (x is 0) */
 62:   }

 64:   KSP_PCApply(ksp,Z,R);                   /*     r <- M^-1z         */
 65:   VecNorm(R,NORM_2,&rnorm);
 66:   KSPCheckNorm(ksp,rnorm);
 67:   KSPLogResidualHistory(ksp,rnorm);
 68:   KSPMonitor(ksp,0,rnorm);
 69:   ksp->rnorm = rnorm;

 71:   /* test for convergence */
 72:   (*ksp->converged)(ksp,0,rnorm,&ksp->reason,ksp->cnvP);
 73:   if (ksp->reason) return(0);

 75:   VecCopy(R,lcd->P[0]);

 77:   while (!ksp->reason && ksp->its < ksp->max_it) {
 78:     it   = 0;
 79:     KSP_MatMult(ksp,Amat,lcd->P[it],Z);
 80:     KSP_PCApply(ksp,Z,lcd->Q[it]);

 82:     while (!ksp->reason && it < max_k && ksp->its < ksp->max_it) {
 83:       ksp->its++;
 84:       VecDot(lcd->P[it],R,&num);
 85:       VecDot(lcd->P[it],lcd->Q[it], &den);
 86:       KSPCheckDot(ksp,den);
 87:       alfa = num/den;
 88:       VecAXPY(X,alfa,lcd->P[it]);
 89:       VecAXPY(R,-alfa,lcd->Q[it]);
 90:       VecNorm(R,NORM_2,&rnorm);
 91:       KSPCheckNorm(ksp,rnorm);

 93:       ksp->rnorm = rnorm;
 94:       KSPLogResidualHistory(ksp,rnorm);
 95:       KSPMonitor(ksp,ksp->its,rnorm);
 96:       (*ksp->converged)(ksp,ksp->its,rnorm,&ksp->reason,ksp->cnvP);

 98:       if (ksp->reason) break;

100:       VecCopy(R,lcd->P[it+1]);
101:       KSP_MatMult(ksp,Amat,lcd->P[it+1],Z);
102:       KSP_PCApply(ksp,Z,lcd->Q[it+1]);

104:       for (j = 0; j <= it; j++) {
105:         VecDot(lcd->P[j],lcd->Q[it+1],&num);
106:         KSPCheckDot(ksp,num);
107:         VecDot(lcd->P[j],lcd->Q[j],&den);
108:         beta = -num/den;
109:         VecAXPY(lcd->P[it+1],beta,lcd->P[j]);
110:         VecAXPY(lcd->Q[it+1],beta,lcd->Q[j]);
111:       }
112:       it++;
113:     }
114:     VecCopy(lcd->P[it],lcd->P[0]);
115:   }
116:   if (ksp->its >= ksp->max_it && !ksp->reason) ksp->reason = KSP_DIVERGED_ITS;
117:   VecCopy(X,ksp->vec_sol);
118:   return(0);
119: }
120: /*
121:        KSPDestroy_LCD - Frees all memory space used by the Krylov method

123: */
124: PetscErrorCode KSPReset_LCD(KSP ksp)
125: {
126:   KSP_LCD        *lcd = (KSP_LCD*)ksp->data;

130:   if (lcd->P) { VecDestroyVecs(lcd->restart+1,&lcd->P);}
131:   if (lcd->Q) { VecDestroyVecs(lcd->restart+1,&lcd->Q);}
132:   return(0);
133: }


136: PetscErrorCode KSPDestroy_LCD(KSP ksp)
137: {

141:   KSPReset_LCD(ksp);
142:   PetscFree(ksp->data);
143:   return(0);
144: }

146: /*
147:      KSPView_LCD - Prints information about the current Krylov method being used

149:       Currently this only prints information to a file (or stdout) about the
150:       symmetry of the problem. If your Krylov method has special options or
151:       flags that information should be printed here.

153: */
154: PetscErrorCode KSPView_LCD(KSP ksp,PetscViewer viewer)
155: {

157:   KSP_LCD        *lcd = (KSP_LCD*)ksp->data;
159:   PetscBool      iascii;

162:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);
163:   if (iascii) {
164:     PetscViewerASCIIPrintf(viewer,"  restart=%d\n",lcd->restart);
165:     PetscViewerASCIIPrintf(viewer,"  happy breakdown tolerance %g\n",lcd->haptol);
166:   }
167:   return(0);
168: }

170: /*
171:     KSPSetFromOptions_LCD - Checks the options database for options related to the
172:                             LCD method.
173: */
174: PetscErrorCode KSPSetFromOptions_LCD(PetscOptionItems *PetscOptionsObject,KSP ksp)
175: {
177:   PetscBool      flg;
178:   KSP_LCD        *lcd = (KSP_LCD*)ksp->data;

181:   PetscOptionsHead(PetscOptionsObject,"KSP LCD options");
182:   PetscOptionsInt("-ksp_lcd_restart","Number of vectors conjugate","KSPLCDSetRestart",lcd->restart,&lcd->restart,&flg);
183:   if (flg && lcd->restart < 1) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_ARG_OUTOFRANGE,"Restart must be positive");
184:   PetscOptionsReal("-ksp_lcd_haptol","Tolerance for exact convergence (happy ending)","KSPLCDSetHapTol",lcd->haptol,&lcd->haptol,&flg);
185:   if (flg && lcd->haptol < 0.0) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_ARG_OUTOFRANGE,"Tolerance must be non-negative");
186:   return(0);
187: }

189: /*MC
190:      KSPLCD -  Implements the LCD (left conjugate direction) method in PETSc.

192:    Options Database Keys:
193: +   -ksp_lcd_restart - number of vectors conjudate
194: -   -ksp_lcd_haptol - tolerance for exact convergence (happing ending)

196:    Level: beginner

198:     Notes:
199:     Support only for left preconditioning

201:     References:
202: +    1. - J.Y. Yuan, G.H.Golub, R.J. Plemmons, and W.A.G. Cecilio. Semiconjugate
203:      direction methods for real positive definite system. BIT Numerical
204:      Mathematics, 44(1),2004.
205: .    2. - Y. Dai and J.Y. Yuan. Study on semiconjugate direction methods for
206:      nonsymmetric systems. International Journal for Numerical Methods in
207:      Engineering, 60, 2004.
208: .    3. - L. Catabriga, A.L.G.A. Coutinho, and L.P.Franca. Evaluating the LCD
209:      algorithm for solving linear systems of equations arising from implicit
210:      SUPG formulation of compressible flows. International Journal for
211:      Numerical Methods in Engineering, 60, 2004
212: -    4. - L. Catabriga, A. M. P. Valli, B. Z. Melotti, L. M. Pessoa,
213:      A. L. G. A. Coutinho, Performance of LCD iterative method in the finite
214:      element and finite difference solution of convection diffusion
215:      equations,  Communications in Numerical Methods in Engineering, (Early
216:      View).

218:   Contributed by: Lucia Catabriga <luciac@ices.utexas.edu>


221: .seealso:  KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP,
222:            KSPCGSetType(), KSPLCDSetRestart(), KSPLCDSetHapTol()

224: M*/

226: PETSC_EXTERN PetscErrorCode KSPCreate_LCD(KSP ksp)
227: {
229:   KSP_LCD        *lcd;

232:   PetscNewLog(ksp,&lcd);
233:   ksp->data    = (void*)lcd;
234:   KSPSetSupportedNorm(ksp,KSP_NORM_PRECONDITIONED,PC_LEFT,3);
235:   lcd->restart = 30;
236:   lcd->haptol  = 1.0e-30;

238:   /*
239:        Sets the functions that are associated with this data structure
240:        (in C++ this is the same as defining virtual functions)
241:   */
242:   ksp->ops->setup          = KSPSetUp_LCD;
243:   ksp->ops->solve          = KSPSolve_LCD;
244:   ksp->ops->reset          = KSPReset_LCD;
245:   ksp->ops->destroy        = KSPDestroy_LCD;
246:   ksp->ops->view           = KSPView_LCD;
247:   ksp->ops->setfromoptions = KSPSetFromOptions_LCD;
248:   ksp->ops->buildsolution  = KSPBuildSolutionDefault;
249:   ksp->ops->buildresidual  = KSPBuildResidualDefault;
250:   return(0);
251: }