irpjast/qmckl_dgemm.org

QMCkl dgemm

• Fortran interface
• C code

Generated from qmckl_dgemm.org

Fortran interface

! <<header>>

module qmckl_blas
  use :: iso_c_binding

  interface
     subroutine qmckl_dgemm(transa, transb, m, n, k, &
          alpha, A, lda, B, ldb, beta, C, ldc) bind(C)
       use :: iso_c_binding
       implicit none
       character(kind=c_char  ), value :: transa, transb
       integer  (kind=c_int   ), value :: m, n, k, lda, ldb, ldc
       real     (kind=c_double), value :: alpha, beta
       real     (kind=c_double)        :: A(lda,*), B(ldb,*), C(ldc,*)
     end subroutine qmckl_dgemm
  end interface

end module qmckl_blas

TODO C code

To avoid passing too many arguments to recursive subroutines, we put all the arguments in a struct.

struct dgemm_args {
double alpha;
double beta;
double* A;
double* B;
double* C;
int m;
int n;
int k;
int lda;
int ldb;
int ldc;
CBLAS_LAYOUT transa;
CBLAS_LAYOUT transb;
};

The driver routine packs the arguments in the struct and calls the recursive routine.

void qmckl_dgemm(char transa, char transb,
               int m, int n, int k,
               double alpha,
               double* A, int lda,
               double* B, int ldb,
               double beta,
               double* C, int ldc)
{
struct dgemm_args args;

args.alpha = alpha;
args.beta  = beta ;
args.A = A;
args.B = B;
args.C = C;
args.m = m;
args.n = n;
args.k = k;
args.lda = lda;
args.ldb = ldb;
args.ldc = ldc;

if (transa == 'T' || transa == 't') {
  args.transa = CblasTrans;
} else {
  args.transa = CblasNoTrans;
}

CBLAS_LAYOUT tb;
if (transa == 'T' || transa == 't') {
  args.transb = CblasTrans;
} else {
  args.transb = CblasNoTrans;
}

#pragma omp parallel
{
  #pragma omp single
  {
    qmckl_dgemm_rec(args);
  }
  #pragma omp taskwait
}
}

#define MIN_SIZE 512 
#include<stdio.h>

static void qmckl_dgemm_rec(struct dgemm_args args) {

//  printf("%5d %5d\n", args.m, args.n);

if ( (args.m <= MIN_SIZE) || (args.n <= MIN_SIZE)) {
  #pragma omp task
  {
    cblas_dgemm(CblasColMajor, args.transa, args.transb,
                args.m, args.n, args.k, args.alpha,
                args.A, args.lda, args.B, args.ldb,
                args.beta, args.C, args.ldc);
  }
} else {

  int m1 = args.m / 2;
  int m2 = args.m - m1;
  int n1 = args.n / 2;
  int n2 = args.n - n1;
    
  #pragma omp task
  {
    struct dgemm_args args_1 = args;
    args_1.m = m1;
    args_1.n = n1;
    qmckl_dgemm_rec(args_1);
  }
  
  #pragma omp task
  {
    // TODO: assuming 'N', 'N' here
    struct dgemm_args args_2 = args;
    args_2.B = args.B + args.ldb*n1;
    args_2.C = args.C + args.ldc*n1;
    args_2.m = m1;
    args_2.n = n2;
    qmckl_dgemm_rec(args_2);
  }
  
  #pragma omp task
  {
    struct dgemm_args args_3 = args;
    args_3.A = args.A + m1;
    args_3.C = args.C + m1;
    args_3.m = m2;
    args_3.n = n1;
    qmckl_dgemm_rec(args_3);
  }
  
  #pragma omp task
  {
    struct dgemm_args args_4 = args;
    args_4.A = args.A + m1;
    args_4.B = args.B + args.ldb*n1;
    args_4.C = args.C + m1 + args.ldc*n1;
    args_4.m = m2;
    args_4.n = n2;
    qmckl_dgemm_rec(args_4);
  }
}

}

/* <<header>> */

#include <cblas.h>

<<dgemm_args>>

<<dgemm_rec>>

<<dgemm>>