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_info
  7:  */

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


 29:   PetscInitialize(&argc,&args,(char*)0,help);
 30:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

 32:   /* Determine files from which we read the linear systems. */
 33:   PetscOptionsGetString(NULL,"-f",file,PETSC_MAX_PATH_LEN,&flg);
 34:   if (!flg) SETERRQ(PETSC_COMM_WORLD,1,"Must indicate binary file with the -f option");

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

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

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

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

 85:   percent=(PetscReal)nnzA*100/(m*n);
 86:   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);
 87:   percent=(PetscReal)nnzAsp*100/(m*n);
 88:   PetscPrintf(PETSC_COMM_SELF," [%d] Matrix Asp nnzAsp %d, %g percent\n",rank,nnzAsp,percent);

 90:   /* investigate matcoloring for Asp */
 91:   PetscBool Asp_coloring = PETSC_FALSE;
 92:   PetscOptionsHasName(NULL,"-Asp_color",&Asp_coloring);
 93:   if (Asp_coloring) {
 94:     ISColoring    iscoloring;
 95:     MatFDColoring matfdcoloring;
 96:     PetscPrintf(PETSC_COMM_WORLD," Create coloring of Asp...\n");
 97:     MatGetColoring(Asp,MATCOLORINGSL,&iscoloring);
 98:     MatFDColoringCreate(Asp,iscoloring,&matfdcoloring);
 99:     MatFDColoringSetFromOptions(matfdcoloring);
100:     /*MatFDColoringView(matfdcoloring,PETSC_VIEWER_STDOUT_WORLD);*/
101:     ISColoringDestroy(&iscoloring);
102:     MatFDColoringDestroy(&matfdcoloring);
103:   }

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

116:   MatDestroy(&A);
117:   MatDestroy(&Asp);
118:   PetscFinalize();
119:   return 0;
120: }