Import GotoBLAS2 1.13 BSD version codes.
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Xianyi Zhang
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reference/zsprf.f
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213
reference/zsprf.f
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SUBROUTINE ZSPRF( UPLO, N, ALPHA, X, INCX, AP )
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*
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* -- LAPACK auxiliary routine (version 3.1) --
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* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
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* November 2006
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*
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* .. Scalar Arguments ..
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CHARACTER UPLO
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INTEGER INCX, N
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COMPLEX*16 ALPHA
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* ..
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* .. Array Arguments ..
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COMPLEX*16 AP( * ), X( * )
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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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* ZSPR performs the symmetric rank 1 operation
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*
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* A := alpha*x*conjg( x' ) + A,
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*
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* where alpha is a complex scalar, x is an n element vector and A is an
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* n by n symmetric matrix, supplied in packed form.
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*
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* Arguments
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* ==========
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*
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* UPLO (input) CHARACTER*1
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* On entry, UPLO specifies whether the upper or lower
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* triangular part of the matrix A is supplied in the packed
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* array AP as follows:
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*
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* UPLO = 'U' or 'u' The upper triangular part of A is
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* supplied in AP.
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*
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* UPLO = 'L' or 'l' The lower triangular part of A is
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* supplied in AP.
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*
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* Unchanged on exit.
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*
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* N (input) INTEGER
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* On entry, N specifies the order of the matrix A.
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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 (input) COMPLEX*16
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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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* X (input) COMPLEX*16 array, dimension at least
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* ( 1 + ( N - 1 )*abs( INCX ) ).
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* Before entry, the incremented array X must contain the N-
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* element vector x.
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* Unchanged on exit.
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*
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* INCX (input) INTEGER
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* On entry, INCX specifies the increment for the elements of
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* X. INCX must not be zero.
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* Unchanged on exit.
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*
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* AP (input/output) COMPLEX*16 array, dimension at least
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* ( ( N*( N + 1 ) )/2 ).
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* Before entry, with UPLO = 'U' or 'u', the array AP must
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* contain the upper triangular part of the symmetric matrix
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* packed sequentially, column by column, so that AP( 1 )
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* contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 1, 2 )
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* and a( 2, 2 ) respectively, and so on. On exit, the array
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* AP is overwritten by the upper triangular part of the
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* updated matrix.
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* Before entry, with UPLO = 'L' or 'l', the array AP must
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* contain the lower triangular part of the symmetric matrix
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* packed sequentially, column by column, so that AP( 1 )
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* contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 2, 1 )
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* and a( 3, 1 ) respectively, and so on. On exit, the array
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* AP is overwritten by the lower triangular part of the
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* 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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* =====================================================================
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*
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* .. Parameters ..
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COMPLEX*16 ZERO
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PARAMETER ( ZERO = ( 0.0D+0, 0.0D+0 ) )
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* ..
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* .. Local Scalars ..
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INTEGER I, INFO, IX, J, JX, K, KK, KX
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COMPLEX*16 TEMP
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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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* ..
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* .. External Subroutines ..
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EXTERNAL XERBLA
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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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INFO = 0
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IF( .NOT.LSAME( UPLO, 'U' ) .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
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INFO = 1
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ELSE IF( N.LT.0 ) THEN
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INFO = 2
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ELSE IF( INCX.EQ.0 ) THEN
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INFO = 5
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END IF
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IF( INFO.NE.0 ) THEN
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CALL XERBLA( 'ZSPR ', 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. ( ALPHA.EQ.ZERO ) )
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$ RETURN
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*
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* Set the start point in X if the increment is not unity.
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*
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IF( INCX.LE.0 ) THEN
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KX = 1 - ( N-1 )*INCX
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ELSE IF( INCX.NE.1 ) THEN
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KX = 1
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END IF
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*
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* Start the operations. In this version the elements of the array AP
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* are accessed sequentially with one pass through AP.
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*
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KK = 1
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IF( LSAME( UPLO, 'U' ) ) THEN
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*
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* Form A when upper triangle is stored in AP.
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*
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IF( INCX.EQ.1 ) THEN
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DO 20 J = 1, N
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IF( X( J ).NE.ZERO ) THEN
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TEMP = ALPHA*X( J )
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K = KK
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DO 10 I = 1, J - 1
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AP( K ) = AP( K ) + X( I )*TEMP
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K = K + 1
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10 CONTINUE
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AP( KK+J-1 ) = AP( KK+J-1 ) + X( J )*TEMP
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ELSE
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AP( KK+J-1 ) = AP( KK+J-1 )
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END IF
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KK = KK + J
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20 CONTINUE
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ELSE
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JX = KX
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DO 40 J = 1, N
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IF( X( JX ).NE.ZERO ) THEN
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TEMP = ALPHA*X( JX )
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IX = KX
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DO 30 K = KK, KK + J - 2
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AP( K ) = AP( K ) + X( IX )*TEMP
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IX = IX + INCX
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30 CONTINUE
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AP( KK+J-1 ) = AP( KK+J-1 ) + X( JX )*TEMP
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ELSE
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AP( KK+J-1 ) = AP( KK+J-1 )
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END IF
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JX = JX + INCX
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KK = KK + J
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40 CONTINUE
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END IF
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ELSE
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*
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* Form A when lower triangle is stored in AP.
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*
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IF( INCX.EQ.1 ) THEN
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DO 60 J = 1, N
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IF( X( J ).NE.ZERO ) THEN
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TEMP = ALPHA*X( J )
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AP( KK ) = AP( KK ) + TEMP*X( J )
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K = KK + 1
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DO 50 I = J + 1, N
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AP( K ) = AP( K ) + X( I )*TEMP
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K = K + 1
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50 CONTINUE
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ELSE
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AP( KK ) = AP( KK )
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END IF
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KK = KK + N - J + 1
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60 CONTINUE
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ELSE
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JX = KX
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DO 80 J = 1, N
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IF( X( JX ).NE.ZERO ) THEN
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TEMP = ALPHA*X( JX )
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AP( KK ) = AP( KK ) + TEMP*X( JX )
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IX = JX
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DO 70 K = KK + 1, KK + N - J
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IX = IX + INCX
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AP( K ) = AP( K ) + X( IX )*TEMP
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70 CONTINUE
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ELSE
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AP( KK ) = AP( KK )
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END IF
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JX = JX + INCX
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KK = KK + N - J + 1
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80 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 ZSPR
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*
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END
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