GHOST: GHOST 1.1.2 API documentation

#include <ghost.h>

#include <stdio.h>


#define N 4


static int diag(ghost_gidx row, ghost_lidx *rowlen, ghost_gidx *col, void *val, __attribute__((unused)) void *arg)

{

    *rowlen = 1;

    col[0] = row;

    ((double *)val)[0] = (double)(row+1);


    return 0;

}


int main(int argc, char **argv)

{

    ghost_sparsemat *A;

    ghost_densemat *y, *x;

    double zero = 0.;

    char *Astr, *xstr, *ystr;


    ghost_densemat_traits vtraits = GHOST_DENSEMAT_TRAITS_INITIALIZER;


    ghost_sparsemat_traits mtraits = GHOST_SPARSEMAT_TRAITS_INITIALIZER;

    mtraits.datatype = (ghost_datatype)(GHOST_DT_REAL|GHOST_DT_DOUBLE);

    mtraits.flags = GHOST_SPARSEMAT_SAVE_ORIG_COLS; // needed for printing if more than one process


    GHOST_CALL_RETURN(ghost_init(argc,argv));


    // create matrix source

    ghost_sparsemat_src_rowfunc matsrc = GHOST_SPARSEMAT_SRC_ROWFUNC_INITIALIZER;

    matsrc.func = diag;

    matsrc.maxrowlen = 1;

    matsrc.gnrows = N;


    // create sparse matrix A from row-wise source function

    GHOST_CALL_RETURN(ghost_sparsemat_create(&A, NULL, &mtraits, 1));

    GHOST_CALL_RETURN(ghost_sparsemat_init_rowfunc(A,&matsrc,MPI_COMM_WORLD,0.));


    // create and initialize input vector x and output vector y

    GHOST_CALL_RETURN(ghost_densemat_create(&x, ghost_context_max_map(A->context), vtraits));

    GHOST_CALL_RETURN(ghost_densemat_create(&y, ghost_context_max_map(A->context), vtraits));

    GHOST_CALL_RETURN(ghost_densemat_init_rand(x));      // x = random

    GHOST_CALL_RETURN(ghost_densemat_init_val(y,&zero)); // y = 0


    // compute y = A*x

    GHOST_CALL_RETURN(ghost_spmv(y,A,x,GHOST_SPMV_OPTS_INITIALIZER));


    // print y, A and x

    GHOST_CALL_RETURN(ghost_sparsemat_string(&Astr,A,1));

    GHOST_CALL_RETURN(ghost_densemat_string(&xstr,x));

    GHOST_CALL_RETURN(ghost_densemat_string(&ystr,y));

    printf("%s\n=\n%s\n*\n%s\n",ystr,Astr,xstr);


    // clean up

    free(Astr);

    free(xstr);

    free(ystr);

    ghost_sparsemat_destroy(A);

    ghost_densemat_destroy(x);

    ghost_densemat_destroy(y);


    ghost_finalize();


    return 0;

}