Actual source code: ex11.c

petsc-3.6.4 2016-04-12
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  1: static const char help[] = "Solves a Q1-P0 Stokes problem from Underworld.\n\
  2: \n\
  3: You can obtain a sample matrix from http://ftp.mcs.anl.gov/pub/petsc/matrices/underworld32.gz\n\
  4: and run with -f underworld32.gz\n\n";

  6: #include <petscksp.h>
  7: #include <petscdmda.h>

 11: PetscErrorCode LSCLoadTestOperators(Mat *A11,Mat *A12,Mat *A21,Mat *A22,Vec *b1,Vec *b2)
 12: {
 13:   PetscViewer    viewer;
 15:   char           filename[PETSC_MAX_PATH_LEN];
 16:   PetscBool      flg;

 19:   MatCreate(PETSC_COMM_WORLD,A11);
 20:   MatCreate(PETSC_COMM_WORLD,A12);
 21:   MatCreate(PETSC_COMM_WORLD,A21);
 22:   MatCreate(PETSC_COMM_WORLD,A22);
 23:   MatSetOptionsPrefix(*A11,"a11_");
 24:   MatSetOptionsPrefix(*A22,"a22_");
 25:   MatSetFromOptions(*A11);
 26:   MatSetFromOptions(*A22);
 27:   VecCreate(PETSC_COMM_WORLD,b1);
 28:   VecCreate(PETSC_COMM_WORLD,b2);
 29:   /* Load matrices from a Q1-P0 discretisation of variable viscosity Stokes. The matrix blocks are packed into one file. */
 30:   PetscOptionsGetString(NULL,"-f",filename,sizeof(filename),&flg);
 31:   if (!flg) SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_USER,"Must provide a matrix file with -f");
 32:   PetscViewerBinaryOpen(PETSC_COMM_WORLD,filename,FILE_MODE_READ,&viewer);
 33:   MatLoad(*A11,viewer);
 34:   MatLoad(*A12,viewer);
 35:   MatLoad(*A21,viewer);
 36:   MatLoad(*A22,viewer);
 37:   VecLoad(*b1,viewer);
 38:   VecLoad(*b2,viewer);
 39:   PetscViewerDestroy(&viewer);
 40:   return(0);
 41: }

 45: PetscErrorCode LoadTestMatrices(Mat *_A,Vec *_x,Vec *_b,IS *_isu,IS *_isp)
 46: {
 47:   Vec            f,h,x,b,bX[2];
 48:   Mat            A,Auu,Aup,Apu,App,bA[2][2];
 49:   IS             is_u,is_p,bis[2];
 50:   PetscInt       lnu,lnp,nu,np,i,start_u,end_u,start_p,end_p;
 51:   VecScatter     *vscat;
 52:   PetscMPIInt    rank;

 56:   /* fetch test matrices and vectors */
 57:   LSCLoadTestOperators(&Auu,&Aup,&Apu,&App,&f,&h);

 59:   /* build the mat-nest */
 60:   VecGetSize(f,&nu);
 61:   VecGetSize(h,&np);

 63:   VecGetLocalSize(f,&lnu);
 64:   VecGetLocalSize(h,&lnp);

 66:   VecGetOwnershipRange(f,&start_u,&end_u);
 67:   VecGetOwnershipRange(h,&start_p,&end_p);

 69:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
 70:   PetscSynchronizedPrintf(PETSC_COMM_WORLD,"[%d] lnu = %D | lnp = %D \n", rank, lnu, lnp);
 71:   PetscSynchronizedPrintf(PETSC_COMM_WORLD,"[%d] s_u = %D | e_u = %D \n", rank, start_u, end_u);
 72:   PetscSynchronizedPrintf(PETSC_COMM_WORLD,"[%d] s_p = %D | e_p = %D \n", rank, start_p, end_p);
 73:   PetscSynchronizedPrintf(PETSC_COMM_WORLD,"[%d] is_u (offset) = %D \n", rank, start_u+start_p);
 74:   PetscSynchronizedPrintf(PETSC_COMM_WORLD,"[%d] is_p (offset) = %D \n", rank, start_u+start_p+lnu);
 75:   PetscSynchronizedFlush(PETSC_COMM_WORLD,PETSC_STDOUT);

 77:   ISCreateStride(PETSC_COMM_WORLD,lnu,start_u+start_p,1,&is_u);
 78:   ISCreateStride(PETSC_COMM_WORLD,lnp,start_u+start_p+lnu,1,&is_p);

 80:   bis[0]   = is_u; bis[1]   = is_p;
 81:   bA[0][0] = Auu;  bA[0][1] = Aup;
 82:   bA[1][0] = Apu;  bA[1][1] = App;
 83:   MatCreateNest(PETSC_COMM_WORLD,2,bis,2,bis,&bA[0][0],&A);
 84:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
 85:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);

 87:   /* Pull f,h into b */
 88:   MatCreateVecs(A,&b,&x);
 89:   bX[0] = f;  bX[1] = h;
 90:   PetscMalloc1(2,&vscat);
 91:   for (i=0; i<2; i++) {
 92:     VecScatterCreate(b,bis[i],bX[i],NULL,&vscat[i]);
 93:     VecScatterBegin(vscat[i],bX[i],b,INSERT_VALUES,SCATTER_REVERSE);
 94:   }
 95:   for (i=0; i<2; i++) {
 96:     VecScatterEnd(vscat[i],bX[i],b,INSERT_VALUES,SCATTER_REVERSE);
 97:   }

 99:   /* tidy up */
100:   for (i=0; i<2; i++) {
101:     VecScatterDestroy(&vscat[i]);
102:   }
103:   PetscFree(vscat);
104:   MatDestroy(&Auu);
105:   MatDestroy(&Aup);
106:   MatDestroy(&Apu);
107:   MatDestroy(&App);
108:   VecDestroy(&f);
109:   VecDestroy(&h);

111:   *_isu = is_u;
112:   *_isp = is_p;
113:   *_A   = A;
114:   *_x   = x;
115:   *_b   = b;
116:   return(0);
117: }


122: PetscErrorCode port_lsd_bfbt(void)
123: {
124:   Mat            A;
125:   Vec            x,b;
126:   KSP            ksp_A;
127:   PC             pc_A;
128:   IS             isu,isp;

132:   LoadTestMatrices(&A,&x,&b,&isu,&isp);

134:   KSPCreate(PETSC_COMM_WORLD,&ksp_A);
135:   KSPSetOptionsPrefix(ksp_A,"fc_");
136:   KSPSetOperators(ksp_A,A,A);

138:   KSPGetPC(ksp_A,&pc_A);
139:   PCSetType(pc_A,PCFIELDSPLIT);
140:   PCFieldSplitSetBlockSize(pc_A,2);
141:   PCFieldSplitSetIS(pc_A,"velocity",isu);
142:   PCFieldSplitSetIS(pc_A,"pressure",isp);

144:   KSPSetFromOptions(ksp_A);
145:   KSPSolve(ksp_A,b,x);

147:   /* Pull u,p out of x */
148:   {
149:     PetscInt    loc;
150:     PetscReal   max,norm;
151:     PetscScalar sum;
152:     Vec         uvec,pvec;
153:     VecScatter  uscat,pscat;
154:     Mat         A11,A22;

156:     /* grab matrices and create the compatable u,p vectors */
157:     MatGetSubMatrix(A,isu,isu,MAT_INITIAL_MATRIX,&A11);
158:     MatGetSubMatrix(A,isp,isp,MAT_INITIAL_MATRIX,&A22);

160:     MatCreateVecs(A11,&uvec,NULL);
161:     MatCreateVecs(A22,&pvec,NULL);

163:     /* perform the scatter from x -> (u,p) */
164:     VecScatterCreate(x,isu,uvec,NULL,&uscat);
165:     VecScatterBegin(uscat,x,uvec,INSERT_VALUES,SCATTER_FORWARD);
166:     VecScatterEnd(uscat,x,uvec,INSERT_VALUES,SCATTER_FORWARD);

168:     VecScatterCreate(x,isp,pvec,NULL,&pscat);
169:     VecScatterBegin(pscat,x,pvec,INSERT_VALUES,SCATTER_FORWARD);
170:     VecScatterEnd(pscat,x,pvec,INSERT_VALUES,SCATTER_FORWARD);

172:     PetscPrintf(PETSC_COMM_WORLD,"-- vector vector values --\n");
173:     VecMin(uvec,&loc,&max);
174:     PetscPrintf(PETSC_COMM_WORLD,"  Min(u)  = %1.6f [loc=%D]\n",(double)max,loc);
175:     VecMax(uvec,&loc,&max);
176:     PetscPrintf(PETSC_COMM_WORLD,"  Max(u)  = %1.6f [loc=%D]\n",(double)max,loc);
177:     VecNorm(uvec,NORM_2,&norm);
178:     PetscPrintf(PETSC_COMM_WORLD,"  Norm(u) = %1.6f \n",(double)norm);
179:     VecSum(uvec,&sum);
180:     PetscPrintf(PETSC_COMM_WORLD,"  Sum(u)  = %1.6f \n",(double)PetscRealPart(sum));

182:     PetscPrintf(PETSC_COMM_WORLD,"-- pressure vector values --\n");
183:     VecMin(pvec,&loc,&max);
184:     PetscPrintf(PETSC_COMM_WORLD,"  Min(p)  = %1.6f [loc=%D]\n",(double)max,loc);
185:     VecMax(pvec,&loc,&max);
186:     PetscPrintf(PETSC_COMM_WORLD,"  Max(p)  = %1.6f [loc=%D]\n",(double)max,loc);
187:     VecNorm(pvec,NORM_2,&norm);
188:     PetscPrintf(PETSC_COMM_WORLD,"  Norm(p) = %1.6f \n",(double)norm);
189:     VecSum(pvec,&sum);
190:     PetscPrintf(PETSC_COMM_WORLD,"  Sum(p)  = %1.6f \n",(double)PetscRealPart(sum));

192:     PetscPrintf(PETSC_COMM_WORLD,"-- Full vector values --\n");
193:     VecMin(x,&loc,&max);
194:     PetscPrintf(PETSC_COMM_WORLD,"  Min(u,p)  = %1.6f [loc=%D]\n",(double)max,loc);
195:     VecMax(x,&loc,&max);
196:     PetscPrintf(PETSC_COMM_WORLD,"  Max(u,p)  = %1.6f [loc=%D]\n",(double)max,loc);
197:     VecNorm(x,NORM_2,&norm);
198:     PetscPrintf(PETSC_COMM_WORLD,"  Norm(u,p) = %1.6f \n",(double)norm);
199:     VecSum(x,&sum);
200:     PetscPrintf(PETSC_COMM_WORLD,"  Sum(u,p)  = %1.6f \n",(double)PetscRealPart(sum));

202:     VecScatterDestroy(&uscat);
203:     VecScatterDestroy(&pscat);
204:     VecDestroy(&uvec);
205:     VecDestroy(&pvec);
206:     MatDestroy(&A11);
207:     MatDestroy(&A22);
208:   }

210:   KSPDestroy(&ksp_A);
211:   MatDestroy(&A);
212:   VecDestroy(&x);
213:   VecDestroy(&b);
214:   ISDestroy(&isu);
215:   ISDestroy(&isp);
216:   return(0);
217: }


222: int main(int argc,char **argv)
223: {

226:   PetscInitialize(&argc,&argv,0,help);
227:   port_lsd_bfbt();
228:   PetscFinalize();
229:   return 0;
230: }