question about the blacs library in MKL

[Ye_C_1]

I can find a lot of examples use the syntax like Cblacs_get(...), Cblacs_pinfo(...), but I can not find the c-type declaration in the "mkl_cblacs.h". 

Is it legal to use this kind of c-wrapper function in mkl?

[Zhen_Z_Intel]

Hi Ye,

I am afraid there's no function call Cblas_get in MKL, but you could use BLACS_GET which in defined in mkl_blacs.h. They have same functionality. Could you please tell me where you find function called "Cblas_get" ? I know some opensource library, for instance, ACOUSTO redefined scalapack functions which contains Cblas_get, but it is not intel MKL function.

If you would like to use BLACS_GET, please learn more from following link:
https://software.intel.com/en-us/node/522196

Best regards,
Fiona
 

[Ye_C_1]

Fiona Z. (Intel) wrote:

Hi Ye,

I am afraid there's no function call Cblas_get in MKL, but you could use BLACS_GET which in defined in mkl_blacs.h. They have same functionality. Could you please tell me where you find function called "Cblas_get" ? I know some opensource library, for instance, ACOUSTO redefined scalapack functions which contains Cblas_get, but it is not intel MKL function.

If you would like to use BLACS_GET, please learn more from following link:
https://software.intel.com/en-us/node/522196

Best regards,
Fiona
 

I saw an example on intel's form:

#include <stdio.h>

#include <string.h>

#include <stdlib.h>

#include "mpi.h"

#define AA(i,j) AA[(i)*M+(j)]

int main(int argc, char **argv) {

   int i, j, k;

/************  MPI ***************************/

   int myrank_mpi, nprocs_mpi;

   MPI_Init( &argc, &argv);

   MPI_Comm_rank(MPI_COMM_WORLD, &myrank_mpi);

   MPI_Comm_size(MPI_COMM_WORLD, &nprocs_mpi);

/************  BLACS ***************************/

   int ictxt, nprow, npcol, myrow, mycol,nb;

   int info,itemp;

   int ZERO=0,ONE=1;

   nprow = 2; npcol = 2; nb =2;

   Cblacs_pinfo( &myrank_mpi, &nprocs_mpi ) ;

   Cblacs_get( -1, 0, &ictxt );

   Cblacs_gridinit( &ictxt, "Row", nprow, npcol );

   Cblacs_gridinfo( ictxt, &nprow, &npcol, &myrow, &mycol );

   int M=5;

   double *AA = (double*) malloc(M*M*sizeof(double));

   for(i=0;i<M;i++ )

     for(j=0;j<M;j++)

        AA[i*M+j]=(2*i+3*j+1);

   double *X = (double*) malloc(M*sizeof(double));

   X[0]=1;X[1]=1;X[2]=0;X[3]=0;X[4]=1;

   int descA[9],descx[9],descy[9];

   int mA = numroc_( &M, &nb, &myrow, &ZERO, &nprow );

   int nA = numroc_( &M, &nb, &mycol, &ZERO, &npcol );

   int nx = numroc_( &M, &nb, &myrow, &ZERO, &nprow );

   int my = numroc_( &M, &nb, &myrow, &ZERO, &nprow );

   descinit_(descA, &M,   &M,   &nb,  &nb,  &ZERO, &ZERO, &ictxt, &mA,  &info);

   descinit_(descx, &M, &ONE,   &nb, &ONE,  &ZERO, &ZERO, &ictxt, &nx, &info);

   descinit_(descy, &M, &ONE,   &nb, &ONE,  &ZERO, &ZERO, &ictxt, &my, &info);

   double *x = (double*) malloc(nx*sizeof(double));

   double *y = (double*) calloc(my,sizeof(double));

   double *A = (double*) malloc(mA*nA*sizeof(double));

   int sat,sut;

   for(i=0;i<mA;i++)

   for(j=0;j<nA;j++){

                sat= (myrow*nb)+i+(i/nb)*nb;

                sut= (mycol*nb)+j+(j/nb)*nb;

                A[j*mA+i]=AA(sat,sut);

        }

   for(i=0;i<nx;i++){

                sut= (myrow*nb)+i+(i/nb)*nb;

                x=X[sut];

        }

   double alpha = 1.0; double beta = 0.0;

   pdgemv_("N",&M,&M,&alpha,A,&ONE,&ONE,descA,x,&ONE,&ONE,descx,&ONE,&beta,y,&ONE,&ONE,descy,&ONE);

   Cblacs_barrier(ictxt,"A");

   for(i=0;i<my;i++)

   printf("rank=%d %.2f \n", myrank_mpi,y);

   Cblacs_gridexit( 0 );

   MPI_Finalize();

   return 0;

}

It seems to use the Cblacs_....version of the blacs library. Can you explain it more?
 

I gauss the program does not link to the mkl blacs library, but another library in PATH, Is it correct?

[Zhen_Z_Intel]

Hi Ye,

He might use some other library or redefined functions by self. If you could not make sure, you could compile this program, the system will notice undefined reference to "Cblacs_get", "Cblacs_pinfo"...

And there's no function called "pdgemv_" in MKL, the name should be "pdgemv" which is defined in mkl_pblas.h. Please use functions defined in MKL library. Thank you.

[Ye_C_1]

Fiona Z. (Intel) wrote:

Hi Ye,

He might use some other library or redefined functions by self. If you could not make sure, you could compile this program, the system will notice undefined reference to "Cblacs_get", "Cblacs_pinfo"...

And there's no function called "pdgemv_" in MKL, the name should be "pdgemv" which is defined in mkl_pblas.h. Please use functions defined in MKL library. Thank you.

It's clear!

I will just follow the mkl manual.

[Ye_C_1]

Fiona Z. (Intel) wrote:

Hi Ye,

He might use some other library or redefined functions by self. If you could not make sure, you could compile this program, the system will notice undefined reference to "Cblacs_get", "Cblacs_pinfo"...

And there's no function called "pdgemv_" in MKL, the name should be "pdgemv" which is defined in mkl_pblas.h. Please use functions defined in MKL library. Thank you.

It's clear!

I will just follow the mkl manual.