static char help[] = "Reads in a matrix in ASCII MATLAB format (I,J,A), read in vectors rhs and exact_solu in ASCII format.\n\
Writes them using the PETSc sparse format.\n\
Note: I and J start at 1, not 0, use -noshift if indices in file start with zero!\n\
Input parameters are:\n\
  -Ain  <filename> : input matrix in ascii format\n\
  -rhs  <filename> : input rhs in ascii format\n\
  -solu  <filename> : input true solution in ascii format\n\\n";

/*
Example: ./ex78 -Ain Ain -rhs rhs -solu solu -noshift -mat_view
 with the datafiles in the following format:
Ain (I and J start at 0):
------------------------
3 3 6
0 0 1.0
0 1 2.0
1 0 3.0
1 1 4.0
1 2 5.0
2 2 6.0

rhs
---
0 3.0
1 12.0
2 6.0

solu
----
0 1.0
0 1.0
0 1.0
*/

#include <petscmat.h>

int main(int argc, char **args)
{
  Mat         A = NULL;
  Vec         b, u = NULL, u_tmp;
  char        Ain[PETSC_MAX_PATH_LEN], rhs[PETSC_MAX_PATH_LEN], solu[PETSC_MAX_PATH_LEN];
  int         m, n = 0, nz, dummy; /* these are fscaned so kept as int */
  PetscInt    i, col, row, shift = 1, sizes[3], nsizes;
  PetscScalar val;
  PetscReal   res_norm;
  FILE       *Afile, *bfile, *ufile;
  PetscViewer view;
  PetscBool   flg_A, flg_b, flg_u, flg;
  PetscMPIInt size;

  PetscFunctionBeginUser;
  PetscCall(PetscInitialize(&argc, &args, NULL, help));
  PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
  PetscCheck(size == 1, PETSC_COMM_WORLD, PETSC_ERR_WRONG_MPI_SIZE, "This is a uniprocessor example only!");

  /* Read in matrix, rhs and exact solution from ascii files */
  PetscCall(PetscOptionsGetString(NULL, NULL, "-Ain", Ain, sizeof(Ain), &flg_A));
  PetscCall(PetscOptionsHasName(NULL, NULL, "-noshift", &flg));
  if (flg) shift = 0;
  if (flg_A) {
    PetscCall(PetscPrintf(PETSC_COMM_SELF, "\n Read matrix in ascii format ...\n"));
    PetscCall(PetscFOpen(PETSC_COMM_SELF, Ain, "r", &Afile));
    nsizes = 3;
    PetscCall(PetscOptionsGetIntArray(NULL, NULL, "-nosizesinfile", sizes, &nsizes, &flg));
    if (flg) {
      PetscCheck(nsizes == 3, PETSC_COMM_WORLD, PETSC_ERR_USER, "Must pass in three m,n,nz as arguments for -nosizesinfile");
      m  = sizes[0];
      n  = sizes[1];
      nz = sizes[2];
    } else {
      PetscCheck(fscanf(Afile, "%d %d %d", &m, &n, &nz) == 3, PETSC_COMM_SELF, PETSC_ERR_FILE_UNEXPECTED, "Badly formatted input file");
    }
    PetscCall(PetscPrintf(PETSC_COMM_SELF, "m: %d, n: %d, nz: %d \n", m, n, nz));
    PetscCheck(m == n, PETSC_COMM_SELF, PETSC_ERR_ARG_SIZ, "Number of rows, cols must be same for this example");
    PetscCall(MatCreate(PETSC_COMM_SELF, &A));
    PetscCall(MatSetSizes(A, PETSC_DECIDE, PETSC_DECIDE, m, n));
    PetscCall(MatSetFromOptions(A));
    PetscCall(MatSeqAIJSetPreallocation(A, nz / m, NULL));
    PetscCall(MatSetOption(A, MAT_NEW_NONZERO_ALLOCATION_ERR, PETSC_FALSE));

    for (i = 0; i < nz; i++) {
      PetscCheck(fscanf(Afile, "%d %d %le", &row, &col, (double *)&val) == 3, PETSC_COMM_SELF, PETSC_ERR_FILE_UNEXPECTED, "Badly formatted input file");
      row -= shift;
      col -= shift; /* set index set starts at 0 */
      PetscCall(MatSetValues(A, 1, &row, 1, &col, &val, INSERT_VALUES));
    }
    PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
    PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
    fclose(Afile);
  }

  PetscCall(PetscOptionsGetString(NULL, NULL, "-rhs", rhs, sizeof(rhs), &flg_b));
  if (flg_b) {
    PetscCall(VecCreate(PETSC_COMM_SELF, &b));
    PetscCall(VecSetSizes(b, PETSC_DECIDE, n));
    PetscCall(VecSetFromOptions(b));
    PetscCall(PetscPrintf(PETSC_COMM_SELF, "\n Read rhs in ascii format ...\n"));
    PetscCall(PetscFOpen(PETSC_COMM_SELF, rhs, "r", &bfile));
    for (i = 0; i < n; i++) {
      PetscCheck(fscanf(bfile, "%d %le", &dummy, (double *)&val) == 2, PETSC_COMM_SELF, PETSC_ERR_FILE_UNEXPECTED, "Badly formatted input file");
      PetscCall(VecSetValues(b, 1, &i, &val, INSERT_VALUES));
    }
    PetscCall(VecAssemblyBegin(b));
    PetscCall(VecAssemblyEnd(b));
    fclose(bfile);
  }

  PetscCall(PetscOptionsGetString(NULL, NULL, "-solu", solu, sizeof(solu), &flg_u));
  if (flg_u) {
    PetscCall(VecCreate(PETSC_COMM_SELF, &u));
    PetscCall(VecSetSizes(u, PETSC_DECIDE, n));
    PetscCall(VecSetFromOptions(u));
    PetscCall(PetscPrintf(PETSC_COMM_SELF, "\n Read exact solution in ascii format ...\n"));
    PetscCall(PetscFOpen(PETSC_COMM_SELF, solu, "r", &ufile));
    for (i = 0; i < n; i++) {
      PetscCheck(fscanf(ufile, "%d  %le", &dummy, (double *)&val) == 2, PETSC_COMM_SELF, PETSC_ERR_FILE_UNEXPECTED, "Badly formatted input file");
      PetscCall(VecSetValues(u, 1, &i, &val, INSERT_VALUES));
    }
    PetscCall(VecAssemblyBegin(u));
    PetscCall(VecAssemblyEnd(u));
    fclose(ufile);
  }

  /* Write matrix, rhs and exact solution in Petsc binary file */
  PetscCall(PetscPrintf(PETSC_COMM_SELF, "\n Write matrix in binary to 'matrix.dat' ...\n"));
  PetscCall(PetscViewerBinaryOpen(PETSC_COMM_SELF, "matrix.dat", FILE_MODE_WRITE, &view));
  PetscCall(MatView(A, view));

  if (flg_b) { /* Write rhs in Petsc binary file */
    PetscCall(PetscPrintf(PETSC_COMM_SELF, "\n Write rhs in binary to 'matrix.dat' ...\n"));
    PetscCall(VecView(b, view));
  }
  if (flg_u) {
    PetscCall(PetscPrintf(PETSC_COMM_SELF, "\n Write exact solution in binary to 'matrix.dat' ...\n"));
    PetscCall(VecView(u, view));
  }

  /* Check accuracy of the data */
  if (flg_A & flg_b & flg_u) {
    PetscCall(VecDuplicate(u, &u_tmp));
    PetscCall(MatMult(A, u, u_tmp));
    PetscCall(VecAXPY(u_tmp, -1.0, b));
    PetscCall(VecNorm(u_tmp, NORM_2, &res_norm));
    PetscCall(PetscPrintf(PETSC_COMM_SELF, "\n Accuracy of the reading data: | b - A*u |_2 : %g \n", res_norm));
    PetscCall(VecDestroy(&u_tmp));
  }

  PetscCall(MatDestroy(&A));
  if (flg_b) PetscCall(VecDestroy(&b));
  if (flg_u) PetscCall(VecDestroy(&u));
  PetscCall(PetscViewerDestroy(&view));
  PetscCall(PetscFinalize());
  return 0;
}

/*TEST

   build:
      requires: !defined(PETSC_USE_64BIT_INDICES) double !complex

   test:
      requires: datafilespath
      args: -Ain ${DATAFILESPATH}/matrices/indefinite/afiro_A.dat

TEST*/
