PROGRAM CALL_SGEMM
IMPLICIT NONE
INTEGER, PARAMETER :: M=4,N=3,K=2
INTEGER, PARAMETER :: LDA=M+1, LDB=K+1, LDC=M+1
REAL ALPHA, BETA
REAL A(LDA,K), B(LDB,N), C(LDC,N), D(LDC,N)
! A is M by K, B is K by N and C is M by N.
INTEGER I, J
INTERFACE
SUBROUTINE SGEMM(TRANSA,TRANSB,M,N,K,ALPHA,A,LDA,B,LDB,BETA,C,LDC)
IMPLICIT NONE
! .. Scalar Arguments ..
REAL ALPHA,BETA
INTEGER K,LDA,LDB,LDC,M,N
CHARACTER(LEN=*) TRANSA,TRANSB
! ..
! .. Array Arguments ..
REAL A(LDA,*),B(LDB,*),C(LDC,*)
END
END INTERFACE
DO J=1,K
DO I=1,M
A(I,J)=real(I)+real(J)/10.
END DO
END DO
DO J=1,N
DO I=1,K
B(I,J)=real(I)+real(J)/10.
END DO
END DO
ALPHA=0.5
BETA=0.1
C=0.01
D(1:M,1:N)=alpha*matmul(A(1:M,1:K),B(1:K,1:N))+beta*C(1:M,1:N)
CALL SGEMM('No','no',M,N,K,ALPHA,A,LDA,B,LDB,BETA,C,LDC)
D(1:M,1:N)=D(1:M,1:N)-C(1:M,1:N)
! Should have D(1:M,1:N) = C(1:M,1:N) except for rounding errors.
WRITE(*,*) 'Largest difference: ', MAXVAL(ABS(D(1:M,1:N)))
WRITE(*,*) 'Relative error: ', MAXVAL(ABS(D(1:M,1:N)))/MAXVAL(ABS(C(1:M,1:N)))
END PROGRAM
! OUTPUT:
! Values of adjoint flags TRANSA, TRANSB = N,n
! Values of sizes m,n,k,lda,ldb and ldc = 4,3,2,5,3,4
! Values of alpha, beta = 5.000000e-001, 1.000000e-001
!Value of i,j and A(i,j) = 1, 1, 1.100000e+000
!Value of i,j and A(i,j) = 2, 1, 2.100000e+000
!Value of i,j and A(i,j) = 3, 1, 3.100000e+000
!Value of i,j and A(i,j) = 4, 1, 4.100000e+000
!Value of i,j and A(i,j) = 1, 2, 1.200000e+000
!Value of i,j and A(i,j) = 2, 2, 2.200000e+000
!Value of i,j and A(i,j) = 3, 2, 3.200000e+000
!Value of i,j and A(i,j) = 4, 2, 4.200000e+000
!
!Value of i,j and B(i,j) = 1, 1, 1.100000e+000
!Value of i,j and B(i,j) = 2, 1, 2.100000e+000
!Value of i,j and B(i,j) = 1, 2, 1.200000e+000
!Value of i,j and B(i,j) = 2, 2, 2.200000e+000
!Value of i,j and B(i,j) = 1, 3, 1.300000e+000
!Value of i,j and B(i,j) = 2, 3, 2.300000e+000
!Value of i,j and C(i,j) = 1, 1, 1.866000e+00
!Value of i,j and C(i,j) = 2, 1, 3.466000e+00
!Value of i,j and C(i,j) = 3, 1, 5.066000e+00
!Value of i,j and C(i,j) = 4, 1, 6.665999e+00
!Value of i,j and C(i,j) = 1, 2, 1.981000e+00
!Value of i,j and C(i,j) = 2, 2, 3.681000e+00
!Value of i,j and C(i,j) = 3, 2, 5.381001e+00
!Value of i,j and C(i,j) = 4, 2, 7.081000e+00
!Value of i,j and C(i,j) = 1, 3, 2.096000e+00
!Value of i,j and C(i,j) = 2, 3, 3.896000e+00
!Value of i,j and C(i,j) = 3, 3, 5.696000e+00
!Value of i,j and C(i,j) = 4, 3, 7.495999e+00
! Largest difference: 4.7683715E-7
! Relative error: 6.361222E-8
! These values are implementation dependent because
! of rounding effects.
!
! Purpose of SGEMM
! ================
! SGEMM performs one of the matrix-matrix operations
! C := alpha*op( A )*op( B ) + beta*C,
! where op( X ) is one of
! op( X ) = X or op( X ) = X',
! alpha and beta are scalars, and A, B and C are matrices, with op( A )
! an m by k matrix, op( B ) a k by n matrix and C an m by n matrix.
! Arguments of SGEMM
! ==================
! TRANSA - CHARACTER*1.
! On entry, TRANSA specifies the form of op( A ) to be used in
! the matrix multiplication as follows:
! TRANSA = 'N' or 'n', op( A ) = A.
! TRANSA = 'T' or 't', op( A ) = A'.
! TRANSA = 'C' or 'c', op( A ) = A'.
! Unchanged on exit.
! TRANSB - CHARACTER*1.
! On entry, TRANSB specifies the form of op( B ) to be used in
! the matrix multiplication as follows:
! TRANSB = 'N' or 'n', op( B ) = B.
! TRANSB = 'T' or 't', op( B ) = B'.
! TRANSB = 'C' or 'c', op( B ) = B'.
! Unchanged on exit.
! M - INTEGER.
! On entry, M specifies the number of rows of the matrix
! op( A ) and of the matrix C. M must be at least zero.
! Unchanged on exit.
! N - INTEGER.
! On entry, N specifies the number of columns of the matrix
! op( B ) and the number of columns of the matrix C. N must be
! at least zero.
! Unchanged on exit.
! K - INTEGER.
! On entry, K specifies the number of columns of the matrix
! op( A ) and the number of rows of the matrix op( B ). K must
! be at least zero.
! Unchanged on exit.
! ALPHA - REAL .
! On entry, ALPHA specifies the scalar alpha.
! Unchanged on exit.
! A - REAL array of DIMENSION ( LDA, ka ), where ka is
! k when TRANSA = 'N' or 'n', and is m otherwise.
! Before entry with TRANSA = 'N' or 'n', the leading m by k
! part of the array A must contain the matrix A, otherwise
! the leading k by m part of the array A must contain the
! matrix A.
! Unchanged on exit.
! LDA - INTEGER.
! On entry, LDA specifies the first dimension of A as declared
! in the calling (sub) program. When TRANSA = 'N' or 'n' then
! LDA must be at least max( 1, m ), otherwise LDA must be at
! least max( 1, k ).
! Unchanged on exit.
! B - REAL array of DIMENSION ( LDB, kb ), where kb is
! n when TRANSB = 'N' or 'n', and is k otherwise.
! Before entry with TRANSB = 'N' or 'n', the leading k by n
! part of the array B must contain the matrix B, otherwise
! the leading n by k part of the array B must contain the
! matrix B.
! Unchanged on exit.
! LDB - INTEGER.
! On entry, LDB specifies the first dimension of B as declared
! in the calling (sub) program. When TRANSB = 'N' or 'n' then
! LDB must be at least max( 1, k ), otherwise LDB must be at
! least max( 1, n ).
! Unchanged on exit.
! BETA - REAL .
! On entry, BETA specifies the scalar beta. When BETA is
! supplied as zero then C need not be set on input.
! Unchanged on exit.
! C - REAL array of DIMENSION ( LDC, n ).
! Before entry, the leading m by n part of the array C must
! contain the matrix C, except when beta is zero, in which
! case C need not be set on entry.
! On exit, the array C is overwritten by the m by n matrix
! ( alpha*op( A )*op( B ) + beta*C ).
! LDC - INTEGER.
! On entry, LDC specifies the first dimension of C as declared
! in the calling (sub) program. LDC must be at least
! max( 1, m ).
! Unchanged on exit.
! Level 3 Blas routine.