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301 lines
7.6 KiB
301 lines
7.6 KiB
2 years ago
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*> \brief \b SLASRT sorts numbers in increasing or decreasing order.
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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 SLASRT + dependencies
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/slasrt.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/slasrt.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/slasrt.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 SLASRT( ID, N, D, INFO )
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*
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* .. Scalar Arguments ..
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* CHARACTER ID
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* INTEGER INFO, N
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* ..
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* .. Array Arguments ..
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* REAL D( * )
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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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*> Sort the numbers in D in increasing order (if ID = 'I') or
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*> in decreasing order (if ID = 'D' ).
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*>
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*> Use Quick Sort, reverting to Insertion sort on arrays of
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*> size <= 20. Dimension of STACK limits N to about 2**32.
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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] ID
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*> \verbatim
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*> ID is CHARACTER*1
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*> = 'I': sort D in increasing order;
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*> = 'D': sort D in decreasing order.
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*> \endverbatim
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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 length of the array D.
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*> \endverbatim
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*>
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*> \param[in,out] D
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*> \verbatim
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*> D is REAL array, dimension (N)
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*> On entry, the array to be sorted.
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*> On exit, D has been sorted into increasing order
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*> (D(1) <= ... <= D(N) ) or into decreasing order
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*> (D(1) >= ... >= D(N) ), depending on ID.
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*> \endverbatim
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*>
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*> \param[out] INFO
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*> \verbatim
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*> INFO is INTEGER
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*> = 0: successful exit
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*> < 0: if INFO = -i, the i-th argument had an illegal value
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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 auxOTHERcomputational
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*
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* =====================================================================
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SUBROUTINE SLASRT( ID, N, D, INFO )
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*
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* -- LAPACK computational 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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CHARACTER ID
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INTEGER INFO, N
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* ..
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* .. Array Arguments ..
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REAL D( * )
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* ..
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*
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* =====================================================================
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*
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* .. Parameters ..
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INTEGER SELECT
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PARAMETER ( SELECT = 20 )
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* ..
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* .. Local Scalars ..
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INTEGER DIR, ENDD, I, J, START, STKPNT
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REAL D1, D2, D3, DMNMX, TMP
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* ..
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* .. Local Arrays ..
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INTEGER STACK( 2, 32 )
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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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DIR = -1
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IF( LSAME( ID, 'D' ) ) THEN
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DIR = 0
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ELSE IF( LSAME( ID, 'I' ) ) THEN
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DIR = 1
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END IF
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IF( DIR.EQ.-1 ) 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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END IF
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IF( INFO.NE.0 ) THEN
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CALL XERBLA( 'SLASRT', -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.LE.1 )
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$ RETURN
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*
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STKPNT = 1
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STACK( 1, 1 ) = 1
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STACK( 2, 1 ) = N
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10 CONTINUE
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START = STACK( 1, STKPNT )
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ENDD = STACK( 2, STKPNT )
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STKPNT = STKPNT - 1
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IF( ENDD-START.LE.SELECT .AND. ENDD-START.GT.0 ) THEN
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*
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* Do Insertion sort on D( START:ENDD )
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*
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IF( DIR.EQ.0 ) THEN
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*
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* Sort into decreasing order
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*
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DO 30 I = START + 1, ENDD
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DO 20 J = I, START + 1, -1
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IF( D( J ).GT.D( J-1 ) ) THEN
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DMNMX = D( J )
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D( J ) = D( J-1 )
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D( J-1 ) = DMNMX
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ELSE
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GO TO 30
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END IF
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20 CONTINUE
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30 CONTINUE
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*
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ELSE
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*
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* Sort into increasing order
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*
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DO 50 I = START + 1, ENDD
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DO 40 J = I, START + 1, -1
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IF( D( J ).LT.D( J-1 ) ) THEN
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DMNMX = D( J )
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D( J ) = D( J-1 )
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D( J-1 ) = DMNMX
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ELSE
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GO TO 50
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END IF
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40 CONTINUE
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50 CONTINUE
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*
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END IF
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*
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ELSE IF( ENDD-START.GT.SELECT ) THEN
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*
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* Partition D( START:ENDD ) and stack parts, largest one first
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*
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* Choose partition entry as median of 3
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*
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D1 = D( START )
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D2 = D( ENDD )
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I = ( START+ENDD ) / 2
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D3 = D( I )
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IF( D1.LT.D2 ) THEN
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IF( D3.LT.D1 ) THEN
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DMNMX = D1
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ELSE IF( D3.LT.D2 ) THEN
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DMNMX = D3
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ELSE
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DMNMX = D2
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END IF
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ELSE
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IF( D3.LT.D2 ) THEN
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DMNMX = D2
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ELSE IF( D3.LT.D1 ) THEN
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DMNMX = D3
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ELSE
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DMNMX = D1
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END IF
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END IF
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*
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IF( DIR.EQ.0 ) THEN
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*
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* Sort into decreasing order
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*
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I = START - 1
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J = ENDD + 1
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60 CONTINUE
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70 CONTINUE
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J = J - 1
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IF( D( J ).LT.DMNMX )
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$ GO TO 70
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80 CONTINUE
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I = I + 1
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IF( D( I ).GT.DMNMX )
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$ GO TO 80
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IF( I.LT.J ) THEN
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TMP = D( I )
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D( I ) = D( J )
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D( J ) = TMP
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GO TO 60
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END IF
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IF( J-START.GT.ENDD-J-1 ) THEN
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STKPNT = STKPNT + 1
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STACK( 1, STKPNT ) = START
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STACK( 2, STKPNT ) = J
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STKPNT = STKPNT + 1
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STACK( 1, STKPNT ) = J + 1
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STACK( 2, STKPNT ) = ENDD
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ELSE
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STKPNT = STKPNT + 1
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STACK( 1, STKPNT ) = J + 1
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STACK( 2, STKPNT ) = ENDD
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STKPNT = STKPNT + 1
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STACK( 1, STKPNT ) = START
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STACK( 2, STKPNT ) = J
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END IF
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ELSE
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*
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* Sort into increasing order
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*
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I = START - 1
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J = ENDD + 1
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90 CONTINUE
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100 CONTINUE
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J = J - 1
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IF( D( J ).GT.DMNMX )
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$ GO TO 100
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110 CONTINUE
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I = I + 1
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IF( D( I ).LT.DMNMX )
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$ GO TO 110
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IF( I.LT.J ) THEN
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TMP = D( I )
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D( I ) = D( J )
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D( J ) = TMP
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GO TO 90
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END IF
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IF( J-START.GT.ENDD-J-1 ) THEN
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STKPNT = STKPNT + 1
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STACK( 1, STKPNT ) = START
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STACK( 2, STKPNT ) = J
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STKPNT = STKPNT + 1
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STACK( 1, STKPNT ) = J + 1
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STACK( 2, STKPNT ) = ENDD
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ELSE
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STKPNT = STKPNT + 1
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STACK( 1, STKPNT ) = J + 1
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STACK( 2, STKPNT ) = ENDD
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STKPNT = STKPNT + 1
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STACK( 1, STKPNT ) = START
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STACK( 2, STKPNT ) = J
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END IF
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END IF
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END IF
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IF( STKPNT.GT.0 )
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$ GO TO 10
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RETURN
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*
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* End of SLASRT
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*
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END
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