Actual source code: ex16.c

      2: static char help[] = "Reads a matrix from PETSc binary file. Use for view or investigating matrix data structure. \n\n";
      3: /*
      4:  Example:
      5:       ./ex16 -f <matrix file> -a_mat_view draw -draw_pause -1
      6:       ./ex16 -f <matrix file> -a_mat_view ascii::ascii_info
      7:  */

      9: #include <petscmat.h>
     10: int main(int argc,char **args)
     11: {
     12:   Mat               A,Asp;
     13:   PetscViewer       fd;                        /* viewer */
     14:   char              file[PETSC_MAX_PATH_LEN];  /* input file name */
     15:   PetscErrorCode    ierr;
     16:   PetscInt          m,n,rstart,rend;
     17:   PetscBool         flg;
     18:   PetscInt          row,ncols,j,nrows,nnzA=0,nnzAsp=0;
     19:   const PetscInt    *cols;
     20:   const PetscScalar *vals;
     21:   PetscReal         norm,percent,val,dtol=1.e-16;
     22:   PetscMPIInt       rank;
     23:   MatInfo           matinfo;
     24:   PetscInt          Dnnz,Onnz;

     27:   PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
     28:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

     30:   /* Determine files from which we read the linear systems. */
     31:   PetscOptionsGetString(NULL,NULL,"-f",file,sizeof(file),&flg);
     32:   if (!flg) SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_USER,"Must indicate binary file with the -f option");

     34:   /* Open binary file.  Note that we use FILE_MODE_READ to indicate
     35:      reading from this file. */
     36:   PetscViewerBinaryOpen(PETSC_COMM_WORLD,file,FILE_MODE_READ,&fd);

     38:   /* Load the matrix; then destroy the viewer. */
     39:   MatCreate(PETSC_COMM_WORLD,&A);
     40:   MatSetOptionsPrefix(A,"a_");
     41:   MatSetFromOptions(A);
     42:   MatLoad(A,fd);
     43:   PetscViewerDestroy(&fd);
     44:   MatGetSize(A,&m,&n);
     45:   MatGetInfo(A,MAT_LOCAL,&matinfo);
     46:   /*printf("matinfo.nz_used %g\n",matinfo.nz_used);*/

     48:   /* Get a sparse matrix Asp by dumping zero entries of A */
     49:   MatCreate(PETSC_COMM_WORLD,&Asp);
     50:   MatSetSizes(Asp,m,n,PETSC_DECIDE,PETSC_DECIDE);
     51:   MatSetOptionsPrefix(Asp,"asp_");
     52:   MatSetFromOptions(Asp);
     53:   Dnnz = (PetscInt)matinfo.nz_used/m + 1;
     54:   Onnz = Dnnz/2;
     55:   printf("Dnnz %d %d\n",Dnnz,Onnz);
     56:   MatSeqAIJSetPreallocation(Asp,Dnnz,NULL);
     57:   MatMPIAIJSetPreallocation(Asp,Dnnz,NULL,Onnz,NULL);
     58:   /* The allocation above is approximate so we must set this option to be permissive.
     59:    * Real code should preallocate exactly. */
     60:   MatSetOption(Asp,MAT_NEW_NONZERO_LOCATION_ERR,PETSC_FALSE);

     62:   /* Check zero rows */
     63:   MatGetOwnershipRange(A,&rstart,&rend);
     64:   nrows = 0;
     65:   for (row=rstart; row<rend; row++) {
     66:     MatGetRow(A,row,&ncols,&cols,&vals);
     67:     nnzA += ncols;
     68:     norm  = 0.0;
     69:     for (j=0; j<ncols; j++) {
     70:       val = PetscAbsScalar(vals[j]);
     71:       if (norm < val) norm = norm;
     72:       if (val > dtol) {
     73:         MatSetValues(Asp,1,&row,1,&cols[j],&vals[j],INSERT_VALUES);
     74:         nnzAsp++;
     75:       }
     76:     }
     77:     if (!norm) nrows++;
     78:     MatRestoreRow(A,row,&ncols,&cols,&vals);
     79:   }
     80:   MatAssemblyBegin(Asp,MAT_FINAL_ASSEMBLY);
     81:   MatAssemblyEnd(Asp,MAT_FINAL_ASSEMBLY);

     83:   percent=(PetscReal)nnzA*100/(m*n);
     84:   PetscPrintf(PETSC_COMM_SELF," [%d] Matrix A local size %d,%d; nnzA %d, %g percent; No. of zero rows: %d\n",rank,m,n,nnzA,percent,nrows);
     85:   percent=(PetscReal)nnzAsp*100/(m*n);
     86:   PetscPrintf(PETSC_COMM_SELF," [%d] Matrix Asp nnzAsp %d, %g percent\n",rank,nnzAsp,percent);

     88:   /* investigate matcoloring for Asp */
     89:   PetscBool Asp_coloring = PETSC_FALSE;
     90:   PetscOptionsHasName(NULL,NULL,"-Asp_color",&Asp_coloring);
     91:   if (Asp_coloring) {
     92:     MatColoring   mc;
     93:     ISColoring    iscoloring;
     94:     MatFDColoring matfdcoloring;
     95:     PetscPrintf(PETSC_COMM_WORLD," Create coloring of Asp...\n");
     96:     MatColoringCreate(Asp,&mc);
     97:     MatColoringSetType(mc,MATCOLORINGSL);
     98:     MatColoringSetFromOptions(mc);
     99:     MatColoringApply(mc,&iscoloring);
    100:     MatColoringDestroy(&mc);
    101:     MatFDColoringCreate(Asp,iscoloring,&matfdcoloring);
    102:     MatFDColoringSetFromOptions(matfdcoloring);
    103:     MatFDColoringSetUp(Asp,iscoloring,matfdcoloring);
    104:     /*MatFDColoringView(matfdcoloring,PETSC_VIEWER_STDOUT_WORLD);*/
    105:     ISColoringDestroy(&iscoloring);
    106:     MatFDColoringDestroy(&matfdcoloring);
    107:   }

    109:   /* Write Asp in binary for study - see ~petsc/src/mat/tests/ex124.c */
    110:   PetscBool Asp_write = PETSC_FALSE;
    111:   PetscOptionsHasName(NULL,NULL,"-Asp_write",&Asp_write);
    112:   if (Asp_write) {
    113:     PetscViewer viewer;
    114:     PetscPrintf(PETSC_COMM_SELF,"Write Asp into file Asp.dat ...\n");
    115:     PetscViewerBinaryOpen(PETSC_COMM_WORLD,"Asp.dat",FILE_MODE_WRITE,&viewer);
    116:     MatView(Asp,viewer);
    117:     PetscViewerDestroy(&viewer);
    118:   }

    120:   MatDestroy(&A);
    121:   MatDestroy(&Asp);
    122:   PetscFinalize();
    123:   return ierr;
    124: }