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C Example MUMPS

/*
 *  file c_example.c
 *  This file is part of MUMPS 4.10.0
 *  To run: aprun -n 2 ./dsimpletest < input_simpletest_real
 */
/* Example program using the C interface to the
 * double real arithmetic version of MUMPS, dmumps_c.
 * We solve the system A x = RHS with
 *   A = diag(1 2) and RHS = [1 4]^T
 * Solution is [1 2]^T */
#include <stdio.h>
#include <string.h>
#include "mpi.h"
#include "dmumps_c.h"
#define JOB_INIT -1
#define JOB_END -2
#define USE_COMM_WORLD -987654

int main(int argc, char ** argv)
{
  DMUMPS_STRUC_C id;
  int n = 2;
  int nz = 2;
  int irn[] = {1,2};
  int jcn[] = {1,2};
  double a[2];
  double rhs[2];

  int myid, ierr;
  ierr = MPI_Init(&argc, &argv);
  ierr = MPI_Comm_rank(MPI_COMM_WORLD, &myid);
  /* Define A and rhs */
  rhs[0]=1.0;rhs[1]=4.0;
  a[0]=1.0;a[1]=2.0;

  /* Initialize a MUMPS instance. Use MPI_COMM_WORLD */
  id.job=JOB_INIT; id.par=1; id.sym=0;id.comm_fortran=USE_COMM_WORLD;
  dmumps_c(&id);
  /* Define the problem on the host */
  if (myid == 0) {
    id.n = n; id.nz =nz; id.irn=irn; id.jcn=jcn;
    id.a = a; id.rhs = rhs;
  }
#define ICNTL(I) icntl[(I)-1] /* macro s.t. indices match documentation */
/* No outputs */
  id.ICNTL(1)=-1; id.ICNTL(2)=-1; id.ICNTL(3)=-1; id.ICNTL(4)=0;
/* Call the MUMPS package. */
  id.job=6;
  dmumps_c(&id);
  id.job=JOB_END; dmumps_c(&id); /* Terminate instance */
  if (myid == 0) {
    printf("Solution is : (%8.2f  %8.2f)\n", rhs[0],rhs[1]);
  }
  ierr = MPI_Finalize();
  return 0;
}
/*Input data:

5 :N
12 :NZ
1 2 3.0
2 3 -3.0
4 3 2.0
5 5 1.0
2 1 3.0
1 1 2.0
5 2 4.0
3 4 2.0
2 5 6.0
3 2 -1.0
1 3 4.0
3 3 1.0 :values
20.0
24.0
9.0
6.0
13.0 :RHS

 */