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;

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

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

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

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

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

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

 82:   percent=(PetscReal)nnzA*100/(m*n);
 83:   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);
 84:   percent=(PetscReal)nnzAsp*100/(m*n);
 85:   PetscPrintf(PETSC_COMM_SELF," [%d] Matrix Asp nnzAsp %d, %g percent\n",rank,nnzAsp,percent);

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

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

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