295 lines
9.6 KiB
Fortran
295 lines
9.6 KiB
Fortran
SUBROUTINE SSYMMF ( SIDE, UPLO, M, N, ALPHA, A, LDA, B, LDB,
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$ BETA, C, LDC )
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* .. Scalar Arguments ..
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CHARACTER*1 SIDE, UPLO
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INTEGER M, N, LDA, LDB, LDC
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REAL ALPHA, BETA
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* .. Array Arguments ..
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REAL 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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* SSYMM performs one of the matrix-matrix operations
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*
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* C := alpha*A*B + beta*C,
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*
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* or
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*
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* C := alpha*B*A + beta*C,
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*
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* where alpha and beta are scalars, A is a symmetric matrix and B and
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* C are m by n matrices.
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*
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* Parameters
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* ==========
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*
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* SIDE - CHARACTER*1.
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* On entry, SIDE specifies whether the symmetric matrix A
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* appears on the left or right in the operation as follows:
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*
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* SIDE = 'L' or 'l' C := alpha*A*B + beta*C,
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*
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* SIDE = 'R' or 'r' C := alpha*B*A + beta*C,
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*
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* Unchanged on exit.
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*
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* UPLO - CHARACTER*1.
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* On entry, UPLO specifies whether the upper or lower
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* triangular part of the symmetric matrix A is to be
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* referenced as follows:
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*
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* UPLO = 'U' or 'u' Only the upper triangular part of the
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* symmetric matrix is to be referenced.
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*
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* UPLO = 'L' or 'l' Only the lower triangular part of the
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* symmetric matrix is to be referenced.
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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 C.
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* 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 C.
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* N must be at least zero.
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* Unchanged on exit.
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*
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* ALPHA - REAL .
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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 - REAL array of DIMENSION ( LDA, ka ), where ka is
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* m when SIDE = 'L' or 'l' and is n otherwise.
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* Before entry with SIDE = 'L' or 'l', the m by m part of
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* the array A must contain the symmetric matrix, such that
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* when UPLO = 'U' or 'u', the leading m by m upper triangular
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* part of the array A must contain the upper triangular part
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* of the symmetric matrix and the strictly lower triangular
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* part of A is not referenced, and when UPLO = 'L' or 'l',
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* the leading m by m lower triangular part of the array A
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* must contain the lower triangular part of the symmetric
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* matrix and the strictly upper triangular part of A is not
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* referenced.
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* Before entry with SIDE = 'R' or 'r', the n by n part of
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* the array A must contain the symmetric matrix, such that
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* when UPLO = 'U' or 'u', the leading n by n upper triangular
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* part of the array A must contain the upper triangular part
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* of the symmetric matrix and the strictly lower triangular
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* part of A is not referenced, and when UPLO = 'L' or 'l',
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* the leading n by n lower triangular part of the array A
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* must contain the lower triangular part of the symmetric
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* matrix and the strictly upper triangular part of A is not
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* referenced.
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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 SIDE = 'L' or 'l' 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, n ).
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* Unchanged on exit.
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*
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* B - REAL array of DIMENSION ( LDB, n ).
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* Before entry, the leading m by n part of the array B must
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* contain the 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. LDB 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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* BETA - REAL .
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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 - REAL 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 updated
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* matrix.
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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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*
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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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* .. External Functions ..
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LOGICAL LSAME
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EXTERNAL LSAME
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* .. External Subroutines ..
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EXTERNAL XERBLA
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* .. Intrinsic Functions ..
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INTRINSIC MAX
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* .. Local Scalars ..
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LOGICAL UPPER
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INTEGER I, INFO, J, K, NROWA
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REAL TEMP1, TEMP2
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* .. Parameters ..
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REAL ONE , ZERO
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PARAMETER ( ONE = 1.0E+0, ZERO = 0.0E+0 )
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* ..
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* .. Executable Statements ..
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*
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* Set NROWA as the number of rows of A.
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*
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IF( LSAME( SIDE, 'L' ) )THEN
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NROWA = M
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ELSE
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NROWA = N
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END IF
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UPPER = LSAME( UPLO, 'U' )
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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.LSAME( SIDE, 'L' ) ).AND.
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$ ( .NOT.LSAME( SIDE, 'R' ) ) )THEN
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INFO = 1
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ELSE IF( ( .NOT.UPPER ).AND.
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$ ( .NOT.LSAME( UPLO, 'L' ) ) )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( LDA.LT.MAX( 1, NROWA ) )THEN
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INFO = 7
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ELSE IF( LDB.LT.MAX( 1, M ) )THEN
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INFO = 9
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ELSE IF( LDC.LT.MAX( 1, M ) )THEN
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INFO = 12
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END IF
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IF( INFO.NE.0 )THEN
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CALL XERBLA( 'SSYMM ', 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 ).AND.( BETA.EQ.ONE ) ) )
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$ RETURN
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*
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* And when 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( LSAME( SIDE, 'L' ) )THEN
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*
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* Form C := alpha*A*B + beta*C.
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*
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IF( UPPER )THEN
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DO 70, J = 1, N
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DO 60, I = 1, M
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TEMP1 = ALPHA*B( I, J )
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TEMP2 = ZERO
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DO 50, K = 1, I - 1
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C( K, J ) = C( K, J ) + TEMP1 *A( K, I )
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TEMP2 = TEMP2 + B( K, J )*A( K, I )
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50 CONTINUE
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IF( BETA.EQ.ZERO )THEN
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C( I, J ) = TEMP1*A( I, I ) + ALPHA*TEMP2
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ELSE
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C( I, J ) = BETA *C( I, J ) +
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$ TEMP1*A( I, I ) + ALPHA*TEMP2
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END IF
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60 CONTINUE
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70 CONTINUE
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ELSE
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DO 100, J = 1, N
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DO 90, I = M, 1, -1
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TEMP1 = ALPHA*B( I, J )
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TEMP2 = ZERO
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DO 80, K = I + 1, M
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C( K, J ) = C( K, J ) + TEMP1 *A( K, I )
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TEMP2 = TEMP2 + B( K, J )*A( K, I )
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80 CONTINUE
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IF( BETA.EQ.ZERO )THEN
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C( I, J ) = TEMP1*A( I, I ) + ALPHA*TEMP2
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ELSE
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C( I, J ) = BETA *C( I, J ) +
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$ TEMP1*A( I, I ) + ALPHA*TEMP2
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END IF
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90 CONTINUE
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100 CONTINUE
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END IF
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ELSE
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*
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* Form C := alpha*B*A + beta*C.
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*
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DO 170, J = 1, N
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TEMP1 = ALPHA*A( J, J )
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IF( BETA.EQ.ZERO )THEN
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DO 110, I = 1, M
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C( I, J ) = TEMP1*B( I, J )
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110 CONTINUE
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ELSE
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DO 120, I = 1, M
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C( I, J ) = BETA*C( I, J ) + TEMP1*B( I, J )
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120 CONTINUE
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END IF
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DO 140, K = 1, J - 1
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IF( UPPER )THEN
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TEMP1 = ALPHA*A( K, J )
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ELSE
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TEMP1 = ALPHA*A( J, K )
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END IF
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DO 130, I = 1, M
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C( I, J ) = C( I, J ) + TEMP1*B( I, K )
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130 CONTINUE
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140 CONTINUE
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DO 160, K = J + 1, N
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IF( UPPER )THEN
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TEMP1 = ALPHA*A( J, K )
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ELSE
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TEMP1 = ALPHA*A( K, J )
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END IF
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DO 150, I = 1, M
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C( I, J ) = C( I, J ) + TEMP1*B( I, K )
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150 CONTINUE
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160 CONTINUE
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170 CONTINUE
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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 SSYMM .
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*
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END
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