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191 lines
4.9 KiB
191 lines
4.9 KiB
2 years ago
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*> \brief \b SLASWP performs a series of row interchanges on a general rectangular matrix.
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*
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* =========== DOCUMENTATION ===========
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*
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* Online html documentation available at
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* http://www.netlib.org/lapack/explore-html/
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*
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*> \htmlonly
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*> Download SLASWP + dependencies
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/slaswp.f">
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*> [TGZ]</a>
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/slaswp.f">
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*> [ZIP]</a>
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/slaswp.f">
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*> [TXT]</a>
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*> \endhtmlonly
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*
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* Definition:
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* ===========
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*
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* SUBROUTINE SLASWP( N, A, LDA, K1, K2, IPIV, INCX )
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*
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* .. Scalar Arguments ..
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* INTEGER INCX, K1, K2, LDA, N
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* ..
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* .. Array Arguments ..
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* INTEGER IPIV( * )
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* REAL A( LDA, * )
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* ..
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*
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*
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*> \par Purpose:
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* =============
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*>
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*> \verbatim
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*>
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*> SLASWP performs a series of row interchanges on the matrix A.
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*> One row interchange is initiated for each of rows K1 through K2 of A.
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*> \endverbatim
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*
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* Arguments:
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* ==========
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*
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*> \param[in] N
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*> \verbatim
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*> N is INTEGER
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*> The number of columns of the matrix A.
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*> \endverbatim
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*>
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*> \param[in,out] A
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*> \verbatim
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*> A is REAL array, dimension (LDA,N)
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*> On entry, the matrix of column dimension N to which the row
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*> interchanges will be applied.
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*> On exit, the permuted matrix.
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*> \endverbatim
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*>
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*> \param[in] LDA
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*> \verbatim
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*> LDA is INTEGER
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*> The leading dimension of the array A.
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*> \endverbatim
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*>
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*> \param[in] K1
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*> \verbatim
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*> K1 is INTEGER
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*> The first element of IPIV for which a row interchange will
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*> be done.
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*> \endverbatim
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*>
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*> \param[in] K2
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*> \verbatim
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*> K2 is INTEGER
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*> (K2-K1+1) is the number of elements of IPIV for which a row
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*> interchange will be done.
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*> \endverbatim
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*>
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*> \param[in] IPIV
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*> \verbatim
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*> IPIV is INTEGER array, dimension (K1+(K2-K1)*abs(INCX))
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*> The vector of pivot indices. Only the elements in positions
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*> K1 through K1+(K2-K1)*abs(INCX) of IPIV are accessed.
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*> IPIV(K1+(K-K1)*abs(INCX)) = L implies rows K and L are to be
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*> interchanged.
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*> \endverbatim
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*>
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*> \param[in] INCX
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*> \verbatim
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*> INCX is INTEGER
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*> The increment between successive values of IPIV. If INCX
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*> is negative, the pivots are applied in reverse order.
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*> \endverbatim
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*
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* Authors:
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* ========
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*
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*> \author Univ. of Tennessee
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*> \author Univ. of California Berkeley
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*> \author Univ. of Colorado Denver
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*> \author NAG Ltd.
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*
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*> \ingroup realOTHERauxiliary
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*
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*> \par Further Details:
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* =====================
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*>
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*> \verbatim
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*>
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*> Modified by
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*> R. C. Whaley, Computer Science Dept., Univ. of Tenn., Knoxville, USA
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*> \endverbatim
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*>
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* =====================================================================
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SUBROUTINE SLASWP( N, A, LDA, K1, K2, IPIV, INCX )
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*
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* -- LAPACK auxiliary routine --
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* -- LAPACK is a software package provided by Univ. of Tennessee, --
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* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
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*
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* .. Scalar Arguments ..
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INTEGER INCX, K1, K2, LDA, N
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* ..
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* .. Array Arguments ..
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INTEGER IPIV( * )
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REAL A( LDA, * )
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* ..
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*
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* =====================================================================
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*
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* .. Local Scalars ..
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INTEGER I, I1, I2, INC, IP, IX, IX0, J, K, N32
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REAL TEMP
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* ..
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* .. Executable Statements ..
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*
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* Interchange row I with row IPIV(K1+(I-K1)*abs(INCX)) for each of rows
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* K1 through K2.
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*
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IF( INCX.GT.0 ) THEN
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IX0 = K1
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I1 = K1
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I2 = K2
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INC = 1
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ELSE IF( INCX.LT.0 ) THEN
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IX0 = K1 + ( K1-K2 )*INCX
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I1 = K2
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I2 = K1
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INC = -1
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ELSE
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RETURN
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END IF
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*
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N32 = ( N / 32 )*32
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IF( N32.NE.0 ) THEN
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DO 30 J = 1, N32, 32
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IX = IX0
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DO 20 I = I1, I2, INC
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IP = IPIV( IX )
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IF( IP.NE.I ) THEN
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DO 10 K = J, J + 31
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TEMP = A( I, K )
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A( I, K ) = A( IP, K )
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A( IP, K ) = TEMP
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10 CONTINUE
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END IF
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IX = IX + INCX
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20 CONTINUE
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30 CONTINUE
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END IF
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IF( N32.NE.N ) THEN
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N32 = N32 + 1
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IX = IX0
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DO 50 I = I1, I2, INC
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IP = IPIV( IX )
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IF( IP.NE.I ) THEN
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DO 40 K = N32, N
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TEMP = A( I, K )
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A( I, K ) = A( IP, K )
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A( IP, K ) = TEMP
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40 CONTINUE
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END IF
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IX = IX + INCX
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50 CONTINUE
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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 SLASWP
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*
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END
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