329 lines
11 KiB
Fortran
329 lines
11 KiB
Fortran
SUBROUTINE CHERKF ( UPLO, TRANS, N, K, ALPHA, A, LDA,
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$ BETA, C, LDC )
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* .. Scalar Arguments ..
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CHARACTER*1 UPLO, TRANS
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INTEGER N, K, LDA, LDC
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REAL ALPHA, BETA
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* .. Array Arguments ..
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COMPLEX A( LDA, * ), 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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* CHERK performs one of the hermitian rank k operations
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*
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* C := alpha*A*conjg( A' ) + beta*C,
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*
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* or
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*
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* C := alpha*conjg( A' )*A + beta*C,
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*
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* where alpha and beta are real scalars, C is an n by n hermitian
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* matrix and A is an n by k matrix in the first case and a k by n
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* matrix in the second case.
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*
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* Parameters
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* ==========
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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 array C is to be referenced as
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* follows:
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*
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* UPLO = 'U' or 'u' Only the upper triangular part of C
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* is to be referenced.
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*
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* UPLO = 'L' or 'l' Only the lower triangular part of C
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* is to be referenced.
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*
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* Unchanged on exit.
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*
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* TRANS - CHARACTER*1.
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* On entry, TRANS specifies the operation to be performed as
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* follows:
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*
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* TRANS = 'N' or 'n' C := alpha*A*conjg( A' ) + beta*C.
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*
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* TRANS = 'C' or 'c' C := alpha*conjg( A' )*A + beta*C.
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*
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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 order 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 with TRANS = 'N' or 'n', K specifies the number
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* of columns of the matrix A, and on entry with
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* TRANS = 'C' or 'c', K specifies the number of rows of the
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* matrix A. K 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 - COMPLEX array of DIMENSION ( LDA, ka ), where ka is
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* k when TRANS = 'N' or 'n', and is n otherwise.
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* Before entry with TRANS = 'N' or 'n', the leading n 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 n 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 TRANS = 'N' or 'n'
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* then LDA must be at least max( 1, n ), otherwise LDA must
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* be at least max( 1, k ).
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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.
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* Unchanged on exit.
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*
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* C - COMPLEX array of DIMENSION ( LDC, n ).
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* Before entry with UPLO = 'U' or 'u', the leading n by n
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* upper triangular part of the array C must contain the upper
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* triangular part of the hermitian matrix and the strictly
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* lower triangular part of C is not referenced. On exit, the
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* upper triangular part of the array C is overwritten by the
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* upper triangular part of the updated matrix.
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* Before entry with UPLO = 'L' or 'l', the leading n by n
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* lower triangular part of the array C must contain the lower
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* triangular part of the hermitian matrix and the strictly
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* upper triangular part of C is not referenced. On exit, the
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* lower triangular part of the array C is overwritten by the
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* lower triangular part of the updated matrix.
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* Note that the imaginary parts of the diagonal elements need
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* not be set, they are assumed to be zero, and on exit they
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* are set to zero.
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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, n ).
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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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* -- Modified 8-Nov-93 to set C(J,J) to REAL( C(J,J) ) when BETA = 1.
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* Ed Anderson, Cray Research Inc.
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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 CMPLX, CONJG, MAX, REAL
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* .. Local Scalars ..
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LOGICAL UPPER
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INTEGER I, INFO, J, L, NROWA
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REAL RTEMP
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COMPLEX TEMP
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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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* Test the input parameters.
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*
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IF( LSAME( TRANS, 'N' ) )THEN
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NROWA = N
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ELSE
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NROWA = K
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END IF
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UPPER = LSAME( UPLO, 'U' )
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*
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INFO = 0
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IF( ( .NOT.UPPER ).AND.
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$ ( .NOT.LSAME( UPLO , 'L' ) ) )THEN
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INFO = 1
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ELSE IF( ( .NOT.LSAME( TRANS, 'N' ) ).AND.
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$ ( .NOT.LSAME( TRANS, 'C' ) ) )THEN
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INFO = 2
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ELSE IF( N .LT.0 )THEN
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INFO = 3
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ELSE IF( K .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( LDC.LT.MAX( 1, N ) )THEN
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INFO = 10
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END IF
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IF( INFO.NE.0 )THEN
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CALL XERBLA( 'CHERK ', 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( ( N.EQ.0 ).OR.
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$ ( ( ( ALPHA.EQ.ZERO ).OR.( K.EQ.0 ) ).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( UPPER )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, J
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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, J - 1
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C( I, J ) = BETA*C( I, J )
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30 CONTINUE
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C( J, J ) = BETA*REAL( C( J, J ) )
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40 CONTINUE
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END IF
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ELSE
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IF( BETA.EQ.ZERO )THEN
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DO 60, J = 1, N
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DO 50, I = J, N
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C( I, J ) = ZERO
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50 CONTINUE
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60 CONTINUE
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ELSE
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DO 80, J = 1, N
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C( J, J ) = BETA*REAL( C( J, J ) )
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DO 70, I = J + 1, N
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C( I, J ) = BETA*C( I, J )
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70 CONTINUE
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80 CONTINUE
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END IF
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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( TRANS, 'N' ) )THEN
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*
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* Form C := alpha*A*conjg( A' ) + beta*C.
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*
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IF( UPPER )THEN
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DO 130, J = 1, N
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IF( BETA.EQ.ZERO )THEN
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DO 90, I = 1, J
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C( I, J ) = ZERO
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90 CONTINUE
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ELSE IF( BETA.NE.ONE )THEN
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DO 100, I = 1, J - 1
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C( I, J ) = BETA*C( I, J )
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100 CONTINUE
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C( J, J ) = BETA*REAL( C( J, J ) )
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ELSE
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C( J, J ) = REAL( C( J, J ) )
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END IF
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DO 120, L = 1, K
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IF( A( J, L ).NE.CMPLX( ZERO ) )THEN
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TEMP = ALPHA*CONJG( A( J, L ) )
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DO 110, I = 1, J - 1
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C( I, J ) = C( I, J ) + TEMP*A( I, L )
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110 CONTINUE
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C( J, J ) = REAL( C( J, J ) ) +
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$ REAL( TEMP*A( I, L ) )
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END IF
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120 CONTINUE
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130 CONTINUE
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ELSE
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DO 180, J = 1, N
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IF( BETA.EQ.ZERO )THEN
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DO 140, I = J, N
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C( I, J ) = ZERO
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140 CONTINUE
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ELSE IF( BETA.NE.ONE )THEN
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C( J, J ) = BETA*REAL( C( J, J ) )
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DO 150, I = J + 1, N
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C( I, J ) = BETA*C( I, J )
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150 CONTINUE
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ELSE
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C( J, J ) = REAL( C( J, J ) )
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END IF
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DO 170, L = 1, K
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IF( A( J, L ).NE.CMPLX( ZERO ) )THEN
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TEMP = ALPHA*CONJG( A( J, L ) )
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C( J, J ) = REAL( C( J, J ) ) +
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$ REAL( TEMP*A( J, L ) )
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DO 160, I = J + 1, N
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C( I, J ) = C( I, J ) + TEMP*A( I, L )
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160 CONTINUE
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END IF
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170 CONTINUE
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180 CONTINUE
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END IF
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ELSE
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*
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* Form C := alpha*conjg( A' )*A + beta*C.
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*
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IF( UPPER )THEN
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DO 220, J = 1, N
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DO 200, I = 1, J - 1
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TEMP = ZERO
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DO 190, L = 1, K
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TEMP = TEMP + CONJG( A( L, I ) )*A( L, J )
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190 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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200 CONTINUE
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RTEMP = ZERO
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DO 210, L = 1, K
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RTEMP = RTEMP + CONJG( A( L, J ) )*A( L, J )
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210 CONTINUE
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IF( BETA.EQ.ZERO )THEN
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C( J, J ) = ALPHA*RTEMP
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ELSE
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C( J, J ) = ALPHA*RTEMP + BETA*REAL( C( J, J ) )
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END IF
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220 CONTINUE
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ELSE
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DO 260, J = 1, N
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RTEMP = ZERO
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DO 230, L = 1, K
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RTEMP = RTEMP + CONJG( A( L, J ) )*A( L, J )
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230 CONTINUE
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IF( BETA.EQ.ZERO )THEN
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C( J, J ) = ALPHA*RTEMP
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ELSE
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C( J, J ) = ALPHA*RTEMP + BETA*REAL( C( J, J ) )
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END IF
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DO 250, I = J + 1, N
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TEMP = ZERO
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DO 240, L = 1, K
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TEMP = TEMP + CONJG( A( L, I ) )*A( L, J )
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240 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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250 CONTINUE
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260 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 CHERK .
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*
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END
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