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,PETSC_MAX_PATH_LEN,&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: }