Actual source code: bqpip.c

petsc-3.6.1 2015-08-06
Report Typos and Errors
  1: #include <../src/tao/bound/impls/bqpip/bqpip.h>
  2: #include <petscksp.h>

  6: static PetscErrorCode TaoSetUp_BQPIP(Tao tao)
  7: {
  8:   TAO_BQPIP      *qp =(TAO_BQPIP*)tao->data;

 12:   /* Set pointers to Data */
 13:   VecGetSize(tao->solution,&qp->n);

 15:   /* Allocate some arrays */
 16:   if (!tao->gradient) {
 17:       VecDuplicate(tao->solution, &tao->gradient);
 18:   }
 19:   if (!tao->stepdirection) {
 20:       VecDuplicate(tao->solution, &tao->stepdirection);
 21:   }
 22:   if (!tao->XL) {
 23:       VecDuplicate(tao->solution, &tao->XL);
 24:       VecSet(tao->XL, -1.0e-20);
 25:   }
 26:   if (!tao->XU) {
 27:       VecDuplicate(tao->solution, &tao->XU);
 28:       VecSet(tao->XU, 1.0e20);
 29:   }

 31:   VecDuplicate(tao->solution, &qp->Work);
 32:   VecDuplicate(tao->solution, &qp->XU);
 33:   VecDuplicate(tao->solution, &qp->XL);
 34:   VecDuplicate(tao->solution, &qp->HDiag);
 35:   VecDuplicate(tao->solution, &qp->DiagAxpy);
 36:   VecDuplicate(tao->solution, &qp->RHS);
 37:   VecDuplicate(tao->solution, &qp->RHS2);
 38:   VecDuplicate(tao->solution, &qp->C0);

 40:   VecDuplicate(tao->solution, &qp->G);
 41:   VecDuplicate(tao->solution, &qp->DG);
 42:   VecDuplicate(tao->solution, &qp->S);
 43:   VecDuplicate(tao->solution, &qp->Z);
 44:   VecDuplicate(tao->solution, &qp->DZ);
 45:   VecDuplicate(tao->solution, &qp->GZwork);
 46:   VecDuplicate(tao->solution, &qp->R3);

 48:   VecDuplicate(tao->solution, &qp->T);
 49:   VecDuplicate(tao->solution, &qp->DT);
 50:   VecDuplicate(tao->solution, &qp->DS);
 51:   VecDuplicate(tao->solution, &qp->TSwork);
 52:   VecDuplicate(tao->solution, &qp->R5);
 53:   qp->m=2*qp->n;
 54:   return(0);
 55: }

 59: static PetscErrorCode  QPIPSetInitialPoint(TAO_BQPIP *qp, Tao tao)
 60: {
 62:   PetscReal      two=2.0,p01=1;
 63:   PetscReal      gap1,gap2,fff,mu;

 66:   /* Compute function, Gradient R=Hx+b, and Hessian */
 67:   TaoComputeVariableBounds(tao);
 68:   VecMedian(qp->XL, tao->solution, qp->XU, tao->solution);
 69:   MatMult(tao->hessian, tao->solution, tao->gradient);
 70:   VecCopy(qp->C0, qp->Work);
 71:   VecAXPY(qp->Work, 0.5, tao->gradient);
 72:   VecAXPY(tao->gradient, 1.0, qp->C0);
 73:   VecDot(tao->solution, qp->Work, &fff);
 74:   qp->pobj = fff + qp->c;

 76:   /* Initialize Primal Vectors */
 77:   /* T = XU - X; G = X - XL */
 78:   VecCopy(qp->XU, qp->T);
 79:   VecAXPY(qp->T, -1.0, tao->solution);
 80:   VecCopy(tao->solution, qp->G);
 81:   VecAXPY(qp->G, -1.0, qp->XL);

 83:   VecSet(qp->GZwork, p01);
 84:   VecSet(qp->TSwork, p01);

 86:   VecPointwiseMax(qp->G, qp->G, qp->GZwork);
 87:   VecPointwiseMax(qp->T, qp->T, qp->TSwork);

 89:   /* Initialize Dual Variable Vectors */
 90:   VecCopy(qp->G, qp->Z);
 91:   VecReciprocal(qp->Z);

 93:   VecCopy(qp->T, qp->S);
 94:   VecReciprocal(qp->S);

 96:   MatMult(tao->hessian, qp->Work, qp->RHS);
 97:   VecAbs(qp->RHS);
 98:   VecSet(qp->Work, p01);
 99:   VecPointwiseMax(qp->RHS, qp->RHS, qp->Work);

101:   VecPointwiseDivide(qp->RHS, tao->gradient, qp->RHS);
102:   VecNorm(qp->RHS, NORM_1, &gap1);
103:   mu = PetscMin(10.0,(gap1+10.0)/qp->m);

105:   VecScale(qp->S, mu);
106:   VecScale(qp->Z, mu);

108:   VecSet(qp->TSwork, p01);
109:   VecSet(qp->GZwork, p01);
110:   VecPointwiseMax(qp->S, qp->S, qp->TSwork);
111:   VecPointwiseMax(qp->Z, qp->Z, qp->GZwork);

113:   qp->mu=0;qp->dinfeas=1.0;qp->pinfeas=1.0;
114:   while ( (qp->dinfeas+qp->pinfeas)/(qp->m+qp->n) >= qp->mu ){

116:     VecScale(qp->G, two);
117:     VecScale(qp->Z, two);
118:     VecScale(qp->S, two);
119:     VecScale(qp->T, two);

121:     QPIPComputeResidual(qp,tao);

123:     VecCopy(tao->solution, qp->R3);
124:     VecAXPY(qp->R3, -1.0, qp->G);
125:     VecAXPY(qp->R3, -1.0, qp->XL);

127:     VecCopy(tao->solution, qp->R5);
128:     VecAXPY(qp->R5, 1.0, qp->T);
129:     VecAXPY(qp->R5, -1.0, qp->XU);

131:     VecNorm(qp->R3, NORM_INFINITY, &gap1);
132:     VecNorm(qp->R5, NORM_INFINITY, &gap2);
133:     qp->pinfeas=PetscMax(gap1,gap2);

135:     /* Compute the duality gap */
136:     VecDot(qp->G, qp->Z, &gap1);
137:     VecDot(qp->T, qp->S, &gap2);

139:     qp->gap = (gap1+gap2);
140:     qp->dobj = qp->pobj - qp->gap;
141:     if (qp->m>0) qp->mu=qp->gap/(qp->m); else qp->mu=0.0;
142:     qp->rgap=qp->gap/( PetscAbsReal(qp->dobj) + PetscAbsReal(qp->pobj) + 1.0 );
143:   }
144:   return(0);
145: }

149: static PetscErrorCode TaoDestroy_BQPIP(Tao tao)
150: {
151:   TAO_BQPIP      *qp = (TAO_BQPIP*)tao->data;

155:   if (tao->setupcalled) {
156:     VecDestroy(&qp->G);
157:     VecDestroy(&qp->DG);
158:     VecDestroy(&qp->Z);
159:     VecDestroy(&qp->DZ);
160:     VecDestroy(&qp->GZwork);
161:     VecDestroy(&qp->R3);
162:     VecDestroy(&qp->S);
163:     VecDestroy(&qp->DS);
164:     VecDestroy(&qp->T);

166:     VecDestroy(&qp->DT);
167:     VecDestroy(&qp->TSwork);
168:     VecDestroy(&qp->R5);
169:     VecDestroy(&qp->HDiag);
170:     VecDestroy(&qp->Work);
171:     VecDestroy(&qp->XL);
172:     VecDestroy(&qp->XU);
173:     VecDestroy(&qp->DiagAxpy);
174:     VecDestroy(&qp->RHS);
175:     VecDestroy(&qp->RHS2);
176:     VecDestroy(&qp->C0);
177:   }
178:   PetscFree(tao->data);
179:   return(0);
180: }

184: static PetscErrorCode TaoSolve_BQPIP(Tao tao)
185: {
186:   TAO_BQPIP          *qp = (TAO_BQPIP*)tao->data;
187:   PetscErrorCode     ierr;
188:   PetscInt           its;
189:   PetscReal          d1,d2,ksptol,sigma;
190:   PetscReal          sigmamu;
191:   PetscReal          dstep,pstep,step=0;
192:   PetscReal          gap[4];
193:   TaoConvergedReason reason;

196:   qp->dobj           = 0.0;
197:   qp->pobj           = 1.0;
198:   qp->gap            = 10.0;
199:   qp->rgap           = 1.0;
200:   qp->mu             = 1.0;
201:   qp->sigma          = 1.0;
202:   qp->dinfeas        = 1.0;
203:   qp->psteplength    = 0.0;
204:   qp->dsteplength    = 0.0;

206:   /* Tighten infinite bounds, things break when we don't do this
207:     -- see test_bqpip.c
208:   */
209:   VecSet(qp->XU,1.0e20);
210:   VecSet(qp->XL,-1.0e20);
211:   VecPointwiseMax(qp->XL,qp->XL,tao->XL);
212:   VecPointwiseMin(qp->XU,qp->XU,tao->XU);

214:   TaoComputeObjectiveAndGradient(tao,tao->solution,&qp->c,qp->C0);
215:   TaoComputeHessian(tao,tao->solution,tao->hessian,tao->hessian_pre);
216:   MatMult(tao->hessian, tao->solution, qp->Work);
217:   VecDot(tao->solution, qp->Work, &d1);
218:   VecAXPY(qp->C0, -1.0, qp->Work);
219:   VecDot(qp->C0, tao->solution, &d2);
220:   qp->c -= (d1/2.0+d2);
221:   MatGetDiagonal(tao->hessian, qp->HDiag);

223:   QPIPSetInitialPoint(qp,tao);
224:   QPIPComputeResidual(qp,tao);

226:   /* Enter main loop */
227:   while (PETSC_TRUE){

229:     /* Check Stopping Condition      */
230:     TaoMonitor(tao,tao->niter,qp->pobj,PetscSqrtScalar(qp->gap + qp->dinfeas),qp->pinfeas, step, &reason);
231:     if (reason != TAO_CONTINUE_ITERATING) break;
232:     tao->niter++;
233:     tao->ksp_its=0;

235:     /*
236:        Dual Infeasibility Direction should already be in the right
237:        hand side from computing the residuals
238:     */

240:     QPIPComputeNormFromCentralPath(qp,&d1);

242:     if (tao->niter > 0 && (qp->rnorm>5*qp->mu || d1*d1>qp->m*qp->mu*qp->mu) ) {
243:       sigma=1.0;sigmamu=qp->mu;
244:       sigma=0.0;sigmamu=0;
245:     } else {
246:       sigma=0.0;sigmamu=0;
247:     }
248:     VecSet(qp->DZ, sigmamu);
249:     VecSet(qp->DS, sigmamu);

251:     if (sigmamu !=0){
252:       VecPointwiseDivide(qp->DZ, qp->DZ, qp->G);
253:       VecPointwiseDivide(qp->DS, qp->DS, qp->T);
254:       VecCopy(qp->DZ,qp->RHS2);
255:       VecAXPY(qp->RHS2, 1.0, qp->DS);
256:     } else {
257:       VecZeroEntries(qp->RHS2);
258:     }


261:     /*
262:        Compute the Primal Infeasiblitiy RHS and the
263:        Diagonal Matrix to be added to H and store in Work
264:     */
265:     VecPointwiseDivide(qp->DiagAxpy, qp->Z, qp->G);
266:     VecPointwiseMult(qp->GZwork, qp->DiagAxpy, qp->R3);
267:     VecAXPY(qp->RHS, -1.0, qp->GZwork);

269:     VecPointwiseDivide(qp->TSwork, qp->S, qp->T);
270:     VecAXPY(qp->DiagAxpy, 1.0, qp->TSwork);
271:     VecPointwiseMult(qp->TSwork, qp->TSwork, qp->R5);
272:     VecAXPY(qp->RHS, -1.0, qp->TSwork);
273:     VecAXPY(qp->RHS2, 1.0, qp->RHS);

275:     /*  Determine the solving tolerance */
276:     ksptol = qp->mu/10.0;
277:     ksptol = PetscMin(ksptol,0.001);

279:     MatDiagonalSet(tao->hessian, qp->DiagAxpy, ADD_VALUES);
280:     MatAssemblyBegin(tao->hessian,MAT_FINAL_ASSEMBLY);
281:     MatAssemblyEnd(tao->hessian,MAT_FINAL_ASSEMBLY);

283:     KSPSetOperators(tao->ksp, tao->hessian, tao->hessian_pre);
284:     KSPSolve(tao->ksp, qp->RHS, tao->stepdirection);
285:     KSPGetIterationNumber(tao->ksp,&its);
286:     tao->ksp_its+=its;
287:     tao->ksp_tot_its+=its;

289:     VecScale(qp->DiagAxpy, -1.0);
290:     MatDiagonalSet(tao->hessian, qp->DiagAxpy, ADD_VALUES);
291:     MatAssemblyBegin(tao->hessian,MAT_FINAL_ASSEMBLY);
292:     MatAssemblyEnd(tao->hessian,MAT_FINAL_ASSEMBLY);
293:     VecScale(qp->DiagAxpy, -1.0);
294:     QPComputeStepDirection(qp,tao);
295:     QPStepLength(qp);

297:     /* Calculate New Residual R1 in Work vector */
298:     MatMult(tao->hessian, tao->stepdirection, qp->RHS2);
299:     VecAXPY(qp->RHS2, 1.0, qp->DS);
300:     VecAXPY(qp->RHS2, -1.0, qp->DZ);
301:     VecAYPX(qp->RHS2, qp->dsteplength, tao->gradient);

303:     VecNorm(qp->RHS2, NORM_2, &qp->dinfeas);
304:     VecDot(qp->DZ, qp->DG, gap);
305:     VecDot(qp->DS, qp->DT, gap+1);

307:     qp->rnorm=(qp->dinfeas+qp->psteplength*qp->pinfeas)/(qp->m+qp->n);
308:     pstep = qp->psteplength; dstep = qp->dsteplength;
309:     step = PetscMin(qp->psteplength,qp->dsteplength);
310:     sigmamu= ( pstep*pstep*(gap[0]+gap[1]) +
311:                (1 - pstep + pstep*sigma)*qp->gap  )/qp->m;

313:     if (qp->predcorr && step < 0.9){
314:       if (sigmamu < qp->mu){
315:         sigmamu=sigmamu/qp->mu;
316:         sigmamu=sigmamu*sigmamu*sigmamu;
317:       } else {sigmamu = 1.0;}
318:       sigmamu = sigmamu*qp->mu;

320:       /* Compute Corrector Step */
321:       VecPointwiseMult(qp->DZ, qp->DG, qp->DZ);
322:       VecScale(qp->DZ, -1.0);
323:       VecShift(qp->DZ, sigmamu);
324:       VecPointwiseDivide(qp->DZ, qp->DZ, qp->G);

326:       VecPointwiseMult(qp->DS, qp->DS, qp->DT);
327:       VecScale(qp->DS, -1.0);
328:       VecShift(qp->DS, sigmamu);
329:       VecPointwiseDivide(qp->DS, qp->DS, qp->T);

331:       VecCopy(qp->DZ, qp->RHS2);
332:       VecAXPY(qp->RHS2, -1.0, qp->DS);
333:       VecAXPY(qp->RHS2, 1.0, qp->RHS);

335:       /* Approximately solve the linear system */
336:       MatDiagonalSet(tao->hessian, qp->DiagAxpy, ADD_VALUES);
337:       MatAssemblyBegin(tao->hessian,MAT_FINAL_ASSEMBLY);
338:       MatAssemblyEnd(tao->hessian,MAT_FINAL_ASSEMBLY);
339:       KSPSolve(tao->ksp, qp->RHS2, tao->stepdirection);
340:       KSPGetIterationNumber(tao->ksp,&its);
341:       tao->ksp_its+=its;
342:       tao->ksp_tot_its+=its;

344:       MatDiagonalSet(tao->hessian, qp->HDiag, INSERT_VALUES);
345:       MatAssemblyBegin(tao->hessian,MAT_FINAL_ASSEMBLY);
346:       MatAssemblyEnd(tao->hessian,MAT_FINAL_ASSEMBLY);
347:       QPComputeStepDirection(qp,tao);
348:       QPStepLength(qp);

350:     }  /* End Corrector step */


353:     /* Take the step */
354:     pstep = qp->psteplength; dstep = qp->dsteplength;

356:     VecAXPY(qp->Z, dstep, qp->DZ);
357:     VecAXPY(qp->S, dstep, qp->DS);
358:     VecAXPY(tao->solution, dstep, tao->stepdirection);
359:     VecAXPY(qp->G, dstep, qp->DG);
360:     VecAXPY(qp->T, dstep, qp->DT);

362:     /* Compute Residuals */
363:     QPIPComputeResidual(qp,tao);

365:     /* Evaluate quadratic function */
366:     MatMult(tao->hessian, tao->solution, qp->Work);

368:     VecDot(tao->solution, qp->Work, &d1);
369:     VecDot(tao->solution, qp->C0, &d2);
370:     VecDot(qp->G, qp->Z, gap);
371:     VecDot(qp->T, qp->S, gap+1);

373:     qp->pobj=d1/2.0 + d2+qp->c;
374:     /* Compute the duality gap */
375:     qp->gap = (gap[0]+gap[1]);
376:     qp->dobj = qp->pobj - qp->gap;
377:     if (qp->m>0) qp->mu=qp->gap/(qp->m);
378:     qp->rgap=qp->gap/( PetscAbsReal(qp->dobj) + PetscAbsReal(qp->pobj) + 1.0 );
379:   }  /* END MAIN LOOP  */

381:   return(0);
382: }

386: static PetscErrorCode QPComputeStepDirection(TAO_BQPIP *qp, Tao tao)
387: {


392:   /* Calculate DG */
393:   VecCopy(tao->stepdirection, qp->DG);
394:   VecAXPY(qp->DG, 1.0, qp->R3);

396:   /* Calculate DT */
397:   VecCopy(tao->stepdirection, qp->DT);
398:   VecScale(qp->DT, -1.0);
399:   VecAXPY(qp->DT, -1.0, qp->R5);


402:   /* Calculate DZ */
403:   VecAXPY(qp->DZ, -1.0, qp->Z);
404:   VecPointwiseDivide(qp->GZwork, qp->DG, qp->G);
405:   VecPointwiseMult(qp->GZwork, qp->GZwork, qp->Z);
406:   VecAXPY(qp->DZ, -1.0, qp->GZwork);

408:   /* Calculate DS */
409:   VecAXPY(qp->DS, -1.0, qp->S);
410:   VecPointwiseDivide(qp->TSwork, qp->DT, qp->T);
411:   VecPointwiseMult(qp->TSwork, qp->TSwork, qp->S);
412:   VecAXPY(qp->DS, -1.0, qp->TSwork);

414:   return(0);
415: }

419: static PetscErrorCode QPIPComputeResidual(TAO_BQPIP *qp, Tao tao)
420: {
422:   PetscReal dtmp = 1.0 - qp->psteplength;


426:   /* Compute R3 and R5 */

428:   VecScale(qp->R3, dtmp);
429:   VecScale(qp->R5, dtmp);
430:   qp->pinfeas=dtmp*qp->pinfeas;


433:   VecCopy(qp->S, tao->gradient);
434:   VecAXPY(tao->gradient, -1.0, qp->Z);

436:   MatMult(tao->hessian, tao->solution, qp->RHS);
437:   VecScale(qp->RHS, -1.0);
438:   VecAXPY(qp->RHS, -1.0, qp->C0);
439:   VecAXPY(tao->gradient, -1.0, qp->RHS);

441:   VecNorm(tao->gradient, NORM_1, &qp->dinfeas);
442:   qp->rnorm=(qp->dinfeas+qp->pinfeas)/(qp->m+qp->n);

444:   return(0);
445: }

449: static PetscErrorCode QPStepLength(TAO_BQPIP *qp)
450: {
451:   PetscReal tstep1,tstep2,tstep3,tstep4,tstep;

455:   /* Compute stepsize to the boundary */
456:   VecStepMax(qp->G, qp->DG, &tstep1);
457:   VecStepMax(qp->T, qp->DT, &tstep2);
458:   VecStepMax(qp->S, qp->DS, &tstep3);
459:   VecStepMax(qp->Z, qp->DZ, &tstep4);


462:   tstep = PetscMin(tstep1,tstep2);
463:   qp->psteplength = PetscMin(0.95*tstep,1.0);

465:   tstep = PetscMin(tstep3,tstep4);
466:   qp->dsteplength = PetscMin(0.95*tstep,1.0);

468:   qp->psteplength = PetscMin(qp->psteplength,qp->dsteplength);
469:   qp->dsteplength = qp->psteplength;

471:   return(0);
472: }


477: PetscErrorCode TaoComputeDual_BQPIP(Tao tao,Vec DXL, Vec DXU)
478: {
479:   TAO_BQPIP *qp = (TAO_BQPIP*)tao->data;
480:   PetscErrorCode       ierr;

483:   VecCopy(qp->Z, DXL);
484:   VecCopy(qp->S, DXU);
485:   VecScale(DXU, -1.0);
486:   return(0);
487: }


492: PetscErrorCode QPIPComputeNormFromCentralPath(TAO_BQPIP *qp, PetscReal *norm)
493: {
494:   PetscErrorCode       ierr;
495:   PetscReal    gap[2],mu[2], nmu;

498:   VecPointwiseMult(qp->GZwork, qp->G, qp->Z);
499:   VecPointwiseMult(qp->TSwork, qp->T, qp->S);
500:   VecNorm(qp->TSwork, NORM_1, &mu[0]);
501:   VecNorm(qp->GZwork, NORM_1, &mu[1]);

503:   nmu=-(mu[0]+mu[1])/qp->m;

505:   VecShift(qp->GZwork,nmu);
506:   VecShift(qp->TSwork,nmu);

508:   VecNorm(qp->GZwork,NORM_2,&gap[0]);
509:   VecNorm(qp->TSwork,NORM_2,&gap[1]);
510:   gap[0]*=gap[0];
511:   gap[1]*=gap[1];


514:   qp->pathnorm=PetscSqrtScalar( (gap[0]+gap[1]) );
515:   *norm=qp->pathnorm;

517:   return(0);
518: }

522: static PetscErrorCode TaoSetFromOptions_BQPIP(PetscOptions *PetscOptionsObject,Tao tao)
523: {
524:   TAO_BQPIP      *qp = (TAO_BQPIP*)tao->data;

528:   PetscOptionsHead(PetscOptionsObject,"Interior point method for bound constrained quadratic optimization");
529:   PetscOptionsInt("-tao_bqpip_predcorr","Use a predictor-corrector method","",qp->predcorr,&qp->predcorr,0);
530:   PetscOptionsTail();
531:   KSPSetFromOptions(tao->ksp);
532:   return(0);
533: }

537: static PetscErrorCode TaoView_BQPIP(Tao tao, PetscViewer viewer)
538: {
540:   return(0);
541: }

543: /* --------------------------------------------------------- */
544: /*MC
545:  TAOBQPIP - bounded quadratic interior point algorithm for quadratic 
546:     optimization with box constraints.

548:  Notes: This algorithms solves quadratic problems only, the linear Hessian will
549:         only be computed once.

551:  Options Database Keys:
552: . -tao_bqpip_predcorr - use a predictor/corrector method

554:   Level: beginner
555: M*/

559: PETSC_EXTERN PetscErrorCode TaoCreate_BQPIP(Tao tao)
560: {
561:   TAO_BQPIP      *qp;

565:   PetscNewLog(tao,&qp);
566:   tao->ops->setup = TaoSetUp_BQPIP;
567:   tao->ops->solve = TaoSolve_BQPIP;
568:   tao->ops->view = TaoView_BQPIP;
569:   tao->ops->setfromoptions = TaoSetFromOptions_BQPIP;
570:   tao->ops->destroy = TaoDestroy_BQPIP;
571:   tao->ops->computedual = TaoComputeDual_BQPIP;

573:   /* Override default settings (unless already changed) */
574:   if (!tao->max_it_changed) tao->max_it=100;
575:   if (!tao->max_funcs_changed) tao->max_funcs = 500;
576: #if defined(PETSC_USE_REAL_SINGLE)
577:   if (!tao->fatol_changed) tao->fatol=1e-6;
578:   if (!tao->frtol_changed) tao->frtol=1e-6;
579:   if (!tao->catol_changed) tao->catol=1e-6;
580: #else
581:   if (!tao->fatol_changed) tao->fatol=1e-12;
582:   if (!tao->frtol_changed) tao->frtol=1e-12;
583:   if (!tao->catol_changed) tao->catol=1e-12;
584: #endif

586:   /* Initialize pointers and variables */
587:   qp->n              = 0;
588:   qp->m              = 0;
589:   qp->ksp_tol       = 0.1;

591:   qp->predcorr       = 1;
592:   tao->data = (void*)qp;

594:   KSPCreate(((PetscObject)tao)->comm, &tao->ksp);
595:   KSPSetOptionsPrefix(tao->ksp, tao->hdr.prefix);
596:   KSPSetType(tao->ksp, KSPCG);
597:   KSPSetTolerances(tao->ksp, 1e-14, 1e-30, 1e30, PetscMax(10,qp->n));
598:   return(0);
599: }