Actual source code: ex18.c

petsc-3.3-p6 2013-02-11
  2: #if !defined(PETSC_USE_COMPLEX)

  4: static char help[] = "Reads a PETSc matrix and vector from a file and solves a linear system.\n\
  5: Input arguments are:\n\
  6:   -f <input_file> : file to load.  For example see $PETSC_DIR/share/petsc/datafiles/matrices\n\n";

  8: #include <petscmat.h>
  9: #include <petscksp.h>

 13: int main(int argc,char **args)
 14: {
 16:   PetscInt       its,m,n,mvec;
 17:   PetscLogDouble time1,time2,time;
 18:   PetscReal      norm;
 19:   Vec            x,b,u;
 20:   Mat            A;
 21:   KSP            ksp;
 22:   char           file[PETSC_MAX_PATH_LEN];
 23:   PetscViewer    fd;
 24:   PetscLogStage  stage1;
 25: 
 26:   PetscInitialize(&argc,&args,(char *)0,help);

 28:   /* Read matrix and RHS */
 29:   PetscOptionsGetString(PETSC_NULL,"-f",file,PETSC_MAX_PATH_LEN,PETSC_NULL);
 30:   PetscViewerBinaryOpen(PETSC_COMM_WORLD,file,FILE_MODE_READ,&fd);
 31:   MatCreate(PETSC_COMM_WORLD,&A);
 32:   MatSetType(A,MATSEQAIJ);
 33:   MatLoad(A,fd);
 34:   VecCreate(PETSC_COMM_WORLD,&b);
 35:   VecLoad(b,fd);
 36:   PetscViewerDestroy(&fd);

 38:   /* 
 39:      If the load matrix is larger then the vector, due to being padded 
 40:      to match the blocksize then create a new padded vector
 41:   */
 42:   MatGetSize(A,&m,&n);
 43:   VecGetSize(b,&mvec);
 44:   if (m > mvec) {
 45:     Vec    tmp;
 46:     PetscScalar *bold,*bnew;
 47:     /* create a new vector b by padding the old one */
 48:     VecCreate(PETSC_COMM_WORLD,&tmp);
 49:     VecSetSizes(tmp,PETSC_DECIDE,m);
 50:     VecSetFromOptions(tmp);
 51:     VecGetArray(tmp,&bnew);
 52:     VecGetArray(b,&bold);
 53:     PetscMemcpy(bnew,bold,mvec*sizeof(PetscScalar));
 54:     VecDestroy(&b);
 55:     b = tmp;
 56:   }

 58:   /* Set up solution */
 59:   VecDuplicate(b,&x);
 60:   VecDuplicate(b,&u);
 61:   VecSet(x,0.0);

 63:   /* Solve system */
 64:   PetscLogStageRegister("Stage 1",&stage1);
 65:   PetscLogStagePush(stage1);
 66:   KSPCreate(PETSC_COMM_WORLD,&ksp);
 67:   KSPSetOperators(ksp,A,A,DIFFERENT_NONZERO_PATTERN);
 68:   KSPSetFromOptions(ksp);
 69:   PetscGetTime(&time1);
 70:   KSPSolve(ksp,b,x);
 71:   PetscGetTime(&time2);
 72:   time = time2 - time1;
 73:   PetscLogStagePop();

 75:   /* Show result */
 76:   MatMult(A,x,u);
 77:   VecAXPY(u,-1.0,b);
 78:   VecNorm(u,NORM_2,&norm);
 79:   KSPGetIterationNumber(ksp,&its);
 80:   PetscPrintf(PETSC_COMM_WORLD,"Number of iterations = %3D\n",its);
 81:   PetscPrintf(PETSC_COMM_WORLD,"Residual norm %G\n",norm);
 82:   PetscPrintf(PETSC_COMM_WORLD,"Time for solve = %5.2f seconds\n",time);

 84:   /* Cleanup */
 85:   KSPDestroy(&ksp);
 86:   VecDestroy(&x);
 87:   VecDestroy(&b);
 88:   VecDestroy(&u);
 89:   MatDestroy(&A);

 91:   PetscFinalize();
 92:   return 0;
 93: }

 95: #else
 96: #include <stdio.h>
 97: int main(int argc,char **args)
 98: {
 99:   fprintf(stdout,"This example does not work for complex numbers.\n");
100:   return 0;
101: }
102: #endif