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Diffstat (limited to 'src/fortran/blas/dspr2.f')
| -rw-r--r-- | src/fortran/blas/dspr2.f | 229 |
1 files changed, 229 insertions, 0 deletions
diff --git a/src/fortran/blas/dspr2.f b/src/fortran/blas/dspr2.f new file mode 100644 index 0000000..1cfce21 --- /dev/null +++ b/src/fortran/blas/dspr2.f @@ -0,0 +1,229 @@ + SUBROUTINE DSPR2 ( UPLO, N, ALPHA, X, INCX, Y, INCY, AP ) +* .. Scalar Arguments .. + DOUBLE PRECISION ALPHA + INTEGER INCX, INCY, N + CHARACTER*1 UPLO +* .. Array Arguments .. + DOUBLE PRECISION AP( * ), X( * ), Y( * ) +* .. +* +* Purpose +* ======= +* +* DSPR2 performs the symmetric rank 2 operation +* +* A := alpha*x*y' + alpha*y*x' + A, +* +* where alpha is a scalar, x and y are n element vectors and A is an +* n by n symmetric matrix, supplied in packed form. +* +* Parameters +* ========== +* +* UPLO - CHARACTER*1. +* On entry, UPLO specifies whether the upper or lower +* triangular part of the matrix A is supplied in the packed +* array AP as follows: +* +* UPLO = 'U' or 'u' The upper triangular part of A is +* supplied in AP. +* +* UPLO = 'L' or 'l' The lower triangular part of A is +* supplied in AP. +* +* Unchanged on exit. +* +* N - INTEGER. +* On entry, N specifies the order of the matrix A. +* N must be at least zero. +* Unchanged on exit. +* +* ALPHA - DOUBLE PRECISION. +* On entry, ALPHA specifies the scalar alpha. +* Unchanged on exit. +* +* X - DOUBLE PRECISION array of dimension at least +* ( 1 + ( n - 1 )*abs( INCX ) ). +* Before entry, the incremented array X must contain the n +* element vector x. +* Unchanged on exit. +* +* INCX - INTEGER. +* On entry, INCX specifies the increment for the elements of +* X. INCX must not be zero. +* Unchanged on exit. +* +* Y - DOUBLE PRECISION array of dimension at least +* ( 1 + ( n - 1 )*abs( INCY ) ). +* Before entry, the incremented array Y must contain the n +* element vector y. +* Unchanged on exit. +* +* INCY - INTEGER. +* On entry, INCY specifies the increment for the elements of +* Y. INCY must not be zero. +* Unchanged on exit. +* +* AP - DOUBLE PRECISION array of DIMENSION at least +* ( ( n*( n + 1 ) )/2 ). +* Before entry with UPLO = 'U' or 'u', the array AP must +* contain the upper triangular part of the symmetric matrix +* packed sequentially, column by column, so that AP( 1 ) +* contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 1, 2 ) +* and a( 2, 2 ) respectively, and so on. On exit, the array +* AP is overwritten by the upper triangular part of the +* updated matrix. +* Before entry with UPLO = 'L' or 'l', the array AP must +* contain the lower triangular part of the symmetric matrix +* packed sequentially, column by column, so that AP( 1 ) +* contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 2, 1 ) +* and a( 3, 1 ) respectively, and so on. On exit, the array +* AP is overwritten by the lower triangular part of the +* updated matrix. +* +* +* Level 2 Blas routine. +* +* -- Written on 22-October-1986. +* Jack Dongarra, Argonne National Lab. +* Jeremy Du Croz, Nag Central Office. +* Sven Hammarling, Nag Central Office. +* Richard Hanson, Sandia National Labs. +* +* +* .. Parameters .. + DOUBLE PRECISION ZERO + PARAMETER ( ZERO = 0.0D+0 ) +* .. Local Scalars .. + DOUBLE PRECISION TEMP1, TEMP2 + INTEGER I, INFO, IX, IY, J, JX, JY, K, KK, KX, KY +* .. External Functions .. + LOGICAL LSAME + EXTERNAL LSAME +* .. External Subroutines .. + EXTERNAL XERBLA +* .. +* .. Executable Statements .. +* +* Test the input parameters. +* + INFO = 0 + IF ( .NOT.LSAME( UPLO, 'U' ).AND. + $ .NOT.LSAME( UPLO, 'L' ) )THEN + INFO = 1 + ELSE IF( N.LT.0 )THEN + INFO = 2 + ELSE IF( INCX.EQ.0 )THEN + INFO = 5 + ELSE IF( INCY.EQ.0 )THEN + INFO = 7 + END IF + IF( INFO.NE.0 )THEN + CALL XERBLA( 'DSPR2 ', INFO ) + RETURN + END IF +* +* Quick return if possible. +* + IF( ( N.EQ.0 ).OR.( ALPHA.EQ.ZERO ) ) + $ RETURN +* +* Set up the start points in X and Y if the increments are not both +* unity. +* + IF( ( INCX.NE.1 ).OR.( INCY.NE.1 ) )THEN + IF( INCX.GT.0 )THEN + KX = 1 + ELSE + KX = 1 - ( N - 1 )*INCX + END IF + IF( INCY.GT.0 )THEN + KY = 1 + ELSE + KY = 1 - ( N - 1 )*INCY + END IF + JX = KX + JY = KY + END IF +* +* Start the operations. In this version the elements of the array AP +* are accessed sequentially with one pass through AP. +* + KK = 1 + IF( LSAME( UPLO, 'U' ) )THEN +* +* Form A when upper triangle is stored in AP. +* + IF( ( INCX.EQ.1 ).AND.( INCY.EQ.1 ) )THEN + DO 20, J = 1, N + IF( ( X( J ).NE.ZERO ).OR.( Y( J ).NE.ZERO ) )THEN + TEMP1 = ALPHA*Y( J ) + TEMP2 = ALPHA*X( J ) + K = KK + DO 10, I = 1, J + AP( K ) = AP( K ) + X( I )*TEMP1 + Y( I )*TEMP2 + K = K + 1 + 10 CONTINUE + END IF + KK = KK + J + 20 CONTINUE + ELSE + DO 40, J = 1, N + IF( ( X( JX ).NE.ZERO ).OR.( Y( JY ).NE.ZERO ) )THEN + TEMP1 = ALPHA*Y( JY ) + TEMP2 = ALPHA*X( JX ) + IX = KX + IY = KY + DO 30, K = KK, KK + J - 1 + AP( K ) = AP( K ) + X( IX )*TEMP1 + Y( IY )*TEMP2 + IX = IX + INCX + IY = IY + INCY + 30 CONTINUE + END IF + JX = JX + INCX + JY = JY + INCY + KK = KK + J + 40 CONTINUE + END IF + ELSE +* +* Form A when lower triangle is stored in AP. +* + IF( ( INCX.EQ.1 ).AND.( INCY.EQ.1 ) )THEN + DO 60, J = 1, N + IF( ( X( J ).NE.ZERO ).OR.( Y( J ).NE.ZERO ) )THEN + TEMP1 = ALPHA*Y( J ) + TEMP2 = ALPHA*X( J ) + K = KK + DO 50, I = J, N + AP( K ) = AP( K ) + X( I )*TEMP1 + Y( I )*TEMP2 + K = K + 1 + 50 CONTINUE + END IF + KK = KK + N - J + 1 + 60 CONTINUE + ELSE + DO 80, J = 1, N + IF( ( X( JX ).NE.ZERO ).OR.( Y( JY ).NE.ZERO ) )THEN + TEMP1 = ALPHA*Y( JY ) + TEMP2 = ALPHA*X( JX ) + IX = JX + IY = JY + DO 70, K = KK, KK + N - J + AP( K ) = AP( K ) + X( IX )*TEMP1 + Y( IY )*TEMP2 + IX = IX + INCX + IY = IY + INCY + 70 CONTINUE + END IF + JX = JX + INCX + JY = JY + INCY + KK = KK + N - J + 1 + 80 CONTINUE + END IF + END IF +* + RETURN +* +* End of DSPR2 . +* + END |