forked from lijiext/lammps
317 lines
9.5 KiB
Fortran
317 lines
9.5 KiB
Fortran
SUBROUTINE DGEMM(TRANSA,TRANSB,M,N,K,ALPHA,A,LDA,B,LDB,BETA,C,LDC)
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* .. Scalar Arguments ..
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DOUBLE PRECISION ALPHA,BETA
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INTEGER K,LDA,LDB,LDC,M,N
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CHARACTER TRANSA,TRANSB
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* ..
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* .. Array Arguments ..
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DOUBLE PRECISION A(LDA,*),B(LDB,*),C(LDC,*)
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* ..
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*
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* Purpose
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* =======
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*
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* DGEMM performs one of the matrix-matrix operations
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*
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* C := alpha*op( A )*op( B ) + beta*C,
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*
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* where op( X ) is one of
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*
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* op( X ) = X or op( X ) = X',
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*
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* alpha and beta are scalars, and A, B and C are matrices, with op( A )
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* an m by k matrix, op( B ) a k by n matrix and C an m by n matrix.
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*
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* Arguments
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* ==========
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*
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* TRANSA - CHARACTER*1.
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* On entry, TRANSA specifies the form of op( A ) to be used in
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* the matrix multiplication as follows:
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*
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* TRANSA = 'N' or 'n', op( A ) = A.
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*
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* TRANSA = 'T' or 't', op( A ) = A'.
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*
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* TRANSA = 'C' or 'c', op( A ) = A'.
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*
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* Unchanged on exit.
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*
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* TRANSB - CHARACTER*1.
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* On entry, TRANSB specifies the form of op( B ) to be used in
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* the matrix multiplication as follows:
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*
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* TRANSB = 'N' or 'n', op( B ) = B.
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*
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* TRANSB = 'T' or 't', op( B ) = B'.
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*
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* TRANSB = 'C' or 'c', op( B ) = B'.
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*
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* Unchanged on exit.
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*
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* M - INTEGER.
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* On entry, M specifies the number of rows of the matrix
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* op( A ) and of the matrix C. M must be at least zero.
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* Unchanged on exit.
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*
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* N - INTEGER.
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* On entry, N specifies the number of columns of the matrix
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* op( B ) and the number of columns of the matrix C. N must be
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* at least zero.
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* Unchanged on exit.
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*
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* K - INTEGER.
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* On entry, K specifies the number of columns of the matrix
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* op( A ) and the number of rows of the matrix op( B ). K must
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* be at least zero.
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* Unchanged on exit.
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*
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* ALPHA - DOUBLE PRECISION.
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* On entry, ALPHA specifies the scalar alpha.
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* Unchanged on exit.
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*
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* A - DOUBLE PRECISION array of DIMENSION ( LDA, ka ), where ka is
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* k when TRANSA = 'N' or 'n', and is m otherwise.
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* Before entry with TRANSA = 'N' or 'n', the leading m by k
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* part of the array A must contain the matrix A, otherwise
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* the leading k by m part of the array A must contain the
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* matrix A.
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* Unchanged on exit.
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*
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* LDA - INTEGER.
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* On entry, LDA specifies the first dimension of A as declared
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* in the calling (sub) program. When TRANSA = 'N' or 'n' then
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* LDA must be at least max( 1, m ), otherwise LDA must be at
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* least max( 1, k ).
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* Unchanged on exit.
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*
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* B - DOUBLE PRECISION array of DIMENSION ( LDB, kb ), where kb is
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* n when TRANSB = 'N' or 'n', and is k otherwise.
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* Before entry with TRANSB = 'N' or 'n', the leading k by n
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* part of the array B must contain the matrix B, otherwise
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* the leading n by k part of the array B must contain the
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* matrix B.
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* Unchanged on exit.
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*
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* LDB - INTEGER.
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* On entry, LDB specifies the first dimension of B as declared
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* in the calling (sub) program. When TRANSB = 'N' or 'n' then
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* LDB must be at least max( 1, k ), otherwise LDB must be at
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* least max( 1, n ).
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* Unchanged on exit.
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*
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* BETA - DOUBLE PRECISION.
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* On entry, BETA specifies the scalar beta. When BETA is
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* supplied as zero then C need not be set on input.
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* Unchanged on exit.
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*
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* C - DOUBLE PRECISION array of DIMENSION ( LDC, n ).
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* Before entry, the leading m by n part of the array C must
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* contain the matrix C, except when beta is zero, in which
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* case C need not be set on entry.
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* On exit, the array C is overwritten by the m by n matrix
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* ( alpha*op( A )*op( B ) + beta*C ).
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*
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* LDC - INTEGER.
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* On entry, LDC specifies the first dimension of C as declared
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* in the calling (sub) program. LDC must be at least
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* max( 1, m ).
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* Unchanged on exit.
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*
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* Further Details
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* ===============
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*
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* Level 3 Blas routine.
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*
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* -- Written on 8-February-1989.
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* Jack Dongarra, Argonne National Laboratory.
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* Iain Duff, AERE Harwell.
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* Jeremy Du Croz, Numerical Algorithms Group Ltd.
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* Sven Hammarling, Numerical Algorithms Group Ltd.
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*
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* =====================================================================
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*
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* .. External Functions ..
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LOGICAL LSAME
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EXTERNAL LSAME
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* ..
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* .. External Subroutines ..
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EXTERNAL XERBLA
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* ..
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* .. Intrinsic Functions ..
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INTRINSIC MAX
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* ..
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* .. Local Scalars ..
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DOUBLE PRECISION TEMP
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INTEGER I,INFO,J,L,NCOLA,NROWA,NROWB
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LOGICAL NOTA,NOTB
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* ..
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* .. Parameters ..
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DOUBLE PRECISION ONE,ZERO
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PARAMETER (ONE=1.0D+0,ZERO=0.0D+0)
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* ..
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*
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* Set NOTA and NOTB as true if A and B respectively are not
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* transposed and set NROWA, NCOLA and NROWB as the number of rows
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* and columns of A and the number of rows of B respectively.
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*
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NOTA = LSAME(TRANSA,'N')
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NOTB = LSAME(TRANSB,'N')
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IF (NOTA) THEN
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NROWA = M
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NCOLA = K
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ELSE
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NROWA = K
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NCOLA = M
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END IF
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IF (NOTB) THEN
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NROWB = K
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ELSE
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NROWB = N
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END IF
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*
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* Test the input parameters.
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*
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INFO = 0
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IF ((.NOT.NOTA) .AND. (.NOT.LSAME(TRANSA,'C')) .AND.
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+ (.NOT.LSAME(TRANSA,'T'))) THEN
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INFO = 1
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ELSE IF ((.NOT.NOTB) .AND. (.NOT.LSAME(TRANSB,'C')) .AND.
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+ (.NOT.LSAME(TRANSB,'T'))) THEN
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INFO = 2
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ELSE IF (M.LT.0) THEN
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INFO = 3
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ELSE IF (N.LT.0) THEN
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INFO = 4
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ELSE IF (K.LT.0) THEN
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INFO = 5
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ELSE IF (LDA.LT.MAX(1,NROWA)) THEN
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INFO = 8
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ELSE IF (LDB.LT.MAX(1,NROWB)) THEN
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INFO = 10
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ELSE IF (LDC.LT.MAX(1,M)) THEN
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INFO = 13
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END IF
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IF (INFO.NE.0) THEN
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CALL XERBLA('DGEMM ',INFO)
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RETURN
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END IF
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*
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* Quick return if possible.
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*
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IF ((M.EQ.0) .OR. (N.EQ.0) .OR.
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+ (((ALPHA.EQ.ZERO).OR. (K.EQ.0)).AND. (BETA.EQ.ONE))) RETURN
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*
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* And if alpha.eq.zero.
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*
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IF (ALPHA.EQ.ZERO) THEN
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IF (BETA.EQ.ZERO) THEN
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DO 20 J = 1,N
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DO 10 I = 1,M
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C(I,J) = ZERO
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10 CONTINUE
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20 CONTINUE
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ELSE
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DO 40 J = 1,N
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DO 30 I = 1,M
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C(I,J) = BETA*C(I,J)
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30 CONTINUE
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40 CONTINUE
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END IF
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RETURN
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END IF
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*
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* Start the operations.
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*
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IF (NOTB) THEN
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IF (NOTA) THEN
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*
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* Form C := alpha*A*B + beta*C.
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*
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DO 90 J = 1,N
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IF (BETA.EQ.ZERO) THEN
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DO 50 I = 1,M
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C(I,J) = ZERO
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50 CONTINUE
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ELSE IF (BETA.NE.ONE) THEN
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DO 60 I = 1,M
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C(I,J) = BETA*C(I,J)
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60 CONTINUE
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END IF
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DO 80 L = 1,K
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IF (B(L,J).NE.ZERO) THEN
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TEMP = ALPHA*B(L,J)
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DO 70 I = 1,M
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C(I,J) = C(I,J) + TEMP*A(I,L)
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70 CONTINUE
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END IF
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80 CONTINUE
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90 CONTINUE
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ELSE
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*
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* Form C := alpha*A'*B + beta*C
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*
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DO 120 J = 1,N
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DO 110 I = 1,M
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TEMP = ZERO
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DO 100 L = 1,K
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TEMP = TEMP + A(L,I)*B(L,J)
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100 CONTINUE
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IF (BETA.EQ.ZERO) THEN
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C(I,J) = ALPHA*TEMP
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ELSE
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C(I,J) = ALPHA*TEMP + BETA*C(I,J)
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END IF
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110 CONTINUE
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120 CONTINUE
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END IF
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ELSE
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IF (NOTA) THEN
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*
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* Form C := alpha*A*B' + beta*C
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*
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DO 170 J = 1,N
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IF (BETA.EQ.ZERO) THEN
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DO 130 I = 1,M
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C(I,J) = ZERO
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130 CONTINUE
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ELSE IF (BETA.NE.ONE) THEN
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DO 140 I = 1,M
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C(I,J) = BETA*C(I,J)
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140 CONTINUE
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END IF
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DO 160 L = 1,K
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IF (B(J,L).NE.ZERO) THEN
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TEMP = ALPHA*B(J,L)
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DO 150 I = 1,M
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C(I,J) = C(I,J) + TEMP*A(I,L)
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150 CONTINUE
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END IF
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160 CONTINUE
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170 CONTINUE
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ELSE
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*
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* Form C := alpha*A'*B' + beta*C
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*
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DO 200 J = 1,N
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DO 190 I = 1,M
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TEMP = ZERO
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DO 180 L = 1,K
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TEMP = TEMP + A(L,I)*B(J,L)
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180 CONTINUE
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IF (BETA.EQ.ZERO) THEN
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C(I,J) = ALPHA*TEMP
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ELSE
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C(I,J) = ALPHA*TEMP + BETA*C(I,J)
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END IF
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190 CONTINUE
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200 CONTINUE
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END IF
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END IF
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*
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RETURN
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*
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* End of DGEMM .
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*
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END
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