SUBROUTINE DTZSCAL( UPLO, M, N, IOFFD, ALPHA, A, LDA ) * * -- PBLAS auxiliary routine (version 2.0) -- * University of Tennessee, Knoxville, Oak Ridge National Laboratory, * and University of California, Berkeley. * April 1, 1998 * * .. Scalar Arguments .. CHARACTER*1 UPLO INTEGER IOFFD, LDA, M, N DOUBLE PRECISION ALPHA * .. * .. Array Arguments .. DOUBLE PRECISION A( LDA, * ) * .. * * Purpose * ======= * * DTZSCAL scales a two-dimensional array A by the scalar alpha. * * Arguments * ========= * * UPLO (input) CHARACTER*1 * On entry, UPLO specifies which trapezoidal part of the ar- * ray A is to be scaled as follows: * = 'L' or 'l': the lower trapezoid of A is scaled, * = 'U' or 'u': the upper trapezoid of A is scaled, * = 'D' or 'd': diagonal specified by IOFFD is scaled, * Otherwise: all of the array A is scaled. * * M (input) INTEGER * On entry, M specifies the number of rows of the array A. M * must be at least zero. * * N (input) INTEGER * On entry, N specifies the number of columns of the array A. * N must be at least zero. * * IOFFD (input) INTEGER * On entry, IOFFD specifies the position of the offdiagonal de- * limiting the upper and lower trapezoidal part of A as follows * (see the notes below): * * IOFFD = 0 specifies the main diagonal A( i, i ), * with i = 1 ... MIN( M, N ), * IOFFD > 0 specifies the subdiagonal A( i+IOFFD, i ), * with i = 1 ... MIN( M-IOFFD, N ), * IOFFD < 0 specifies the superdiagonal A( i, i-IOFFD ), * with i = 1 ... MIN( M, N+IOFFD ). * * ALPHA (input) DOUBLE PRECISION * On entry, ALPHA specifies the scalar alpha, i.e., the value * by which the diagonal and offdiagonal entries of the array A * as specified by UPLO and IOFFD are scaled. * * A (input/output) DOUBLE PRECISION array * On entry, A is an array of dimension (LDA,N). Before entry * with UPLO = 'U' or 'u', the leading m by n part of the array * A must contain the upper trapezoidal part of the matrix as * specified by IOFFD to be scaled, and the strictly lower tra- * pezoidal part of A is not referenced; When UPLO = 'L' or 'l', * the leading m by n part of the array A must contain the lower * trapezoidal part of the matrix as specified by IOFFD to be * scaled, and the strictly upper trapezoidal part of A is not * referenced. On exit, the entries of the trapezoid part of A * determined by UPLO and IOFFD are scaled. * * LDA (input) INTEGER * On entry, LDA specifies the leading dimension of the array A. * LDA must be at least max( 1, M ). * * Notes * ===== * N N * ---------------------------- ----------- * | d | | | * M | d 'U' | | 'U' | * | 'L' 'D' | |d | * | d | M | d | * ---------------------------- | 'D' | * | d | * IOFFD < 0 | 'L' d | * | d| * N | | * ----------- ----------- * | d 'U'| * | d | IOFFD > 0 * M | 'D' | * | d| N * | 'L' | ---------------------------- * | | | 'U' | * | | |d | * | | | 'D' | * | | | d | * | | |'L' d | * ----------- ---------------------------- * * -- Written on April 1, 1998 by * Antoine Petitet, University of Tennessee, Knoxville 37996, USA. * * ===================================================================== * * .. Parameters .. DOUBLE PRECISION ONE, ZERO PARAMETER ( ONE = 1.0D+0, ZERO = 0.0D+0 ) * .. * .. Local Scalars .. INTEGER J, JTMP, MN * .. * .. External Subroutines .. EXTERNAL DSCAL, DTZPAD * .. * .. External Functions .. LOGICAL LSAME EXTERNAL LSAME * .. * .. Intrinsic Functions .. INTRINSIC MAX, MIN * .. * .. Executable Statements .. * * Quick return if possible * IF( ( M.LE.0 ).OR.( N.LE.0 ).OR.( ALPHA.EQ.ONE ) ) $ RETURN * * Start the operations * IF( ALPHA.EQ.ZERO ) THEN CALL DTZPAD( UPLO, 'N', M, N, IOFFD, ZERO, ZERO, A, LDA ) RETURN END IF * IF( LSAME( UPLO, 'L' ) ) THEN * * Scales the lower triangular part of the array by ALPHA. * MN = MAX( 0, -IOFFD ) DO 10 J = 1, MIN( MN, N ) CALL DSCAL( M, ALPHA, A( 1, J ), 1 ) 10 CONTINUE DO 20 J = MN + 1, MIN( M - IOFFD, N ) JTMP = J + IOFFD IF( M.GE.JTMP ) $ CALL DSCAL( M-JTMP+1, ALPHA, A( JTMP, J ), 1 ) 20 CONTINUE * ELSE IF( LSAME( UPLO, 'U' ) ) THEN * * Scales the upper triangular part of the array by ALPHA. * MN = MIN( M - IOFFD, N ) DO 30 J = MAX( 0, -IOFFD ) + 1, MN CALL DSCAL( J + IOFFD, ALPHA, A( 1, J ), 1 ) 30 CONTINUE DO 40 J = MAX( 0, MN ) + 1, N CALL DSCAL( M, ALPHA, A( 1, J ), 1 ) 40 CONTINUE * ELSE IF( LSAME( UPLO, 'D' ) ) THEN * * Scales the diagonal entries by ALPHA. * DO 50 J = MAX( 0, -IOFFD ) + 1, MIN( M - IOFFD, N ) JTMP = J + IOFFD A( JTMP, J ) = ALPHA * A( JTMP, J ) 50 CONTINUE * ELSE * * Scales the entire array by ALPHA. * DO 60 J = 1, N CALL DSCAL( M, ALPHA, A( 1, J ), 1 ) 60 CONTINUE * END IF * RETURN * * End of DTZSCAL * END