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SUBROUTINE PBSVECADD( ICONTXT, MODE, N, ALPHA, X, INCX, BETA, Y,
$ INCY )
*
* -- PB-BLAS routine (version 2.1) --
* University of Tennessee, Knoxville, Oak Ridge National Laboratory.
* April 28, 1996
*
* .. Scalar Arguments ..
CHARACTER*1 MODE
INTEGER ICONTXT, INCX, INCY, N
REAL ALPHA, BETA
* ..
* .. Array Arguments ..
REAL X( * ), Y( * )
*
* ..
*
* Purpose
* =======
*
* PBSVECADD performs a vector X to be added to Y
* Y := alpha*op(X) + beta*Y,
* where alpha and beta are scalars, and X and Y are n vectors,
* and op(X) = X**H if MODE = 'C',
*
* Arguments
* =========
*
* ICONTXT (input) INTEGER
* ICONTXT is the BLACS mechanism for partitioning communication
* space. A defining property of a context is that a message in
* a context cannot be sent or received in another context. The
* BLACS context includes the definition of a grid, and each
* process' coordinates in it.
*
* MODE (input) CHARACTER*1
* Specifies the transposed, or conjugate transposed vector X
* to be added to the vector Y
* = 'C': Conjugate vector X is added for complex data set.
* Y = alpha * X**H + beta * Y
* ELSE : Vector X is added. Y = alpha*X + beta*Y
* if MODE = 'V', BLAS routine may be used.
*
* N (input) INTEGER
* The number of elements of the vectors X and Y to be added.
* N >= 0.
*
* ALPHA (input) REAL
* ALPHA specifies the scalar alpha.
*
* X (input) REAL array of DIMENSION at least
* ( 1 + ( N - 1 )*abs( INCX ) )
* The incremented array X must contain the vector X.
*
* INCX (input) INTEGER
* INCX specifies the increment for the elements of X.
* INCX <> 0.
*
* BETA (input) REAL
* BETA specifies the scalar beta.
*
* Y (input/output) REAL array of DIMENSION at least
* ( 1 + ( N - 1 )*abs( INCY ) )
* On entry with BETA non-zero, the incremented array Y must
* contain the vector Y.
* On exit, Y is overwritten by the updated vector Y.
*
* INCY - (input) INTEGER
* INCY specifies the increment for the elements of Y.
* INCY <> 0.
*
* =====================================================================
*
* ..
* .. Parameters ..
REAL ZERO, ONE
PARAMETER ( ZERO = 0.0E+0, ONE = 1.0E+0)
* ..
* .. Local Scalars ..
INTEGER I, IX, IY
* ..
* .. External Functions ..
LOGICAL LSAME
EXTERNAL LSAME
* ..
* .. External Subroutines ..
EXTERNAL SSCAL, SCOPY, SAXPY
* ..
* .. Executable Statements ..
*
IF( N.LE.0 .OR. ( ALPHA.EQ.ZERO .AND. BETA.EQ.ONE ) ) RETURN
*
IF( ALPHA.EQ.ZERO ) THEN
IF( BETA.EQ.ZERO ) THEN
IF( INCY.EQ.1 ) THEN
DO 10 I = 1, N
Y( I ) = ZERO
10 CONTINUE
ELSE
IY = 1
DO 20 I = 1, N
Y( IY ) = ZERO
IY = IY + INCY
20 CONTINUE
END IF
*
ELSE
IF( LSAME( MODE, 'V' ) ) THEN
CALL SSCAL( N, BETA, Y, INCY )
ELSE IF( INCY.EQ.1 ) THEN
DO 30 I = 1, N
Y( I ) = BETA * Y( I )
30 CONTINUE
ELSE
IY = 1
DO 40 I = 1, N
Y( IY ) = BETA * Y( IY )
IY = IY + INCY
40 CONTINUE
END IF
END IF
*
ELSE
IF( ALPHA.EQ.ONE ) THEN
IF( BETA.EQ.ZERO ) THEN
IF( LSAME( MODE, 'V' ) ) THEN
CALL SCOPY( N, X, INCX, Y, INCY )
ELSE IF( INCX.EQ.1 .AND. INCY.EQ.1 ) THEN
DO 50 I = 1, N
Y( I ) = X( I )
50 CONTINUE
ELSE
IX = 1
IY = 1
DO 60 I = 1, N
Y( IY ) = X( IX )
IX = IX + INCX
IY = IY + INCY
60 CONTINUE
END IF
*
ELSE IF( BETA.EQ.ONE ) THEN
IF( INCX.EQ.1 .AND. INCY.EQ.1 ) THEN
DO 70 I = 1, N
Y( I ) = X( I ) + Y( I )
70 CONTINUE
ELSE
IX = 1
IY = 1
DO 80 I = 1, N
Y( IY ) = X( IX ) + Y( IY )
IX = IX + INCX
IY = IY + INCY
80 CONTINUE
END IF
*
ELSE
IF( INCX.EQ.1 .AND. INCY.EQ.1 ) THEN
DO 90 I = 1, N
Y( I ) = X( I ) + BETA * Y( I )
90 CONTINUE
ELSE
IX = 1
IY = 1
DO 100 I = 1, N
Y( IY ) = X( IX ) + BETA * Y( IY )
IX = IX + INCX
IY = IY + INCY
100 CONTINUE
END IF
END IF
*
ELSE
IF( BETA.EQ.ZERO ) THEN
IF( INCX.EQ.1 .AND. INCY.EQ.1 ) THEN
DO 110 I = 1, N
Y( I ) = ALPHA * X( I )
110 CONTINUE
ELSE
IX = 1
IY = 1
DO 120 I = 1, N
Y( IY ) = X( IX )
IX = IX + INCX
IY = IY + INCY
120 CONTINUE
END IF
*
ELSE IF( BETA.EQ.ONE ) THEN
IF( LSAME( MODE, 'V' ) ) THEN
CALL SAXPY( N, ALPHA, X, INCX, Y, INCY )
ELSE IF( INCX.EQ.1 .AND. INCY.EQ.1 ) THEN
DO 130 I = 1, N
Y( I ) = ALPHA * X( I ) + Y( I )
130 CONTINUE
ELSE
IX = 1
IY = 1
DO 140 I = 1, N
Y( IY ) = ALPHA * X( IX ) + Y( IY )
IX = IX + INCX
IY = IY + INCY
140 CONTINUE
END IF
*
ELSE
IF( INCX.EQ.1 .AND. INCY.EQ.1 ) THEN
DO 150 I = 1, N
Y( I ) = ALPHA * X( I ) + BETA * Y( I )
150 CONTINUE
ELSE
IX = 1
IY = 1
DO 160 I = 1, N
Y( IY ) = ALPHA * X( IX ) + BETA * Y( IY )
IX = IX + INCX
IY = IY + INCY
160 CONTINUE
END IF
END IF
END IF
END IF
*
RETURN
*
* End of PBSVECADD
*
END
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