记忆 lda LDA in blas level-3 SGEMM cublasGemmex cubulasSgemm

LAPACK: sgemm

subroutine sgemm	(	character 	TRANSA,
                        character 	TRANSB,
                        integer 	M,
                        integer 	N,
                        integer 	K,
                        real 	ALPHA,
                        real, dimension(lda,*) 	A,
                        integer 	LDA,
                        real, dimension(ldb,*) 	B,
                        integer 	LDB,
                        real 	BETA,
                        real, dimension(ldc,*) 	C,
                        integer 	LDC 
                    )		


/***************************************************************************

Purpose:
 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**T,

 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.


TRANSA	
          TRANSA is 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**T.

              TRANSA = 'C' or 'c',  op( A ) = A**T.
[in]	TRANSB	
          TRANSB is 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**T.

              TRANSB = 'C' or 'c',  op( B ) = B**T.
[in]	M	
          M is 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.
[in]	N	
          N is 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.
[in]	K	
          K is 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.
[in]	ALPHA	
          ALPHA is REAL
           On entry, ALPHA specifies the scalar alpha.
[in]	A	
          A is REAL array, 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.
[in]	LDA	
          LDA is 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 ).
[in]	B	
          B is REAL array, 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.
[in]	LDB	
          LDB is 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 ).
[in]	BETA	
          BETA is REAL
           On entry,  BETA  specifies the scalar  beta.  When  BETA  is
           supplied as zero then C need not be set on input.
[in,out]	C	
          C is REAL array, 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 ).
[in]	LDC	
          LDC is 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 ).



*****************************************************************************/

          M is 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.

          LDA is 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 ).

如果A的op是transA=N，那么 lda >= m; 加上无效数据，总数据量 = ( lda * K ) 个元素.

如果A的op是TransA=T，那么一维数组 A 中最初存储的是以 lda >= K 为列长的数据，

总数据量  =  （ lda * m ) 个元素；

所以，需要先将A转置，得到 A_t  =  T(A)  

若：

C(mxn) = T(A(kxm))  *  T(B(nxk))

则：

lda >=k

ldb >= n