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psblas3/base/serial/aux/isr.f

178 lines
5.0 KiB
Fortran

C
C Parallel Sparse BLAS v2.0
C (C) Copyright 2006 Salvatore Filippone University of Rome Tor Vergata
C Alfredo Buttari University of Rome Tor Vergata
C
C Redistribution and use in source and binary forms, with or without
C modification, are permitted provided that the following conditions
C are met:
C 1. Redistributions of source code must retain the above copyright
C notice, this list of conditions and the following disclaimer.
C 2. Redistributions in binary form must reproduce the above copyright
C notice, this list of conditions, and the following disclaimer in the
C documentation and/or other materials provided with the distribution.
C 3. The name of the PSBLAS group or the names of its contributors may
C not be used to endorse or promote products derived from this
C software without specific written permission.
C
C THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
C ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
C TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
C PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE PSBLAS GROUP OR ITS CONTRIBUTORS
C BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
C CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
C SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
C INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
C CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
C ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
C POSSIBILITY OF SUCH DAMAGE.
C
C
SUBROUTINE ISR(N,X)
C
C Quicksort.
C Adapted from a number of sources, including Don Knuth's TAOCP.
C
C .. Scalar Arguments ..
INTEGER N
C ..
C .. Array Arguments ..
INTEGER X(N)
C ..
C .. Local Scalars ..
INTEGER I, J, XX, ILX, IUX, ISTP, PIV, LPIV
INTEGER IT1, N1, N2
INTEGER MAXSTACK,NPARMS,ITHRS
PARAMETER (MAXSTACK=64,NPARMS=3,ITHRS=16)
INTEGER ISTACK(NPARMS,MAXSTACK)
C ..
C
C Small inputs will only get through insertion sort.
C
IF (N.GT.ITHRS) THEN
C
C Init stack pointer
C
ISTP = 1
ISTACK(1,ISTP) = 1
ISTACK(2,ISTP) = N
DO WHILE (ISTP.GT.0)
ILX = ISTACK(1,ISTP)
IUX = ISTACK(2,ISTP)
ISTP = ISTP - 1
c$$$ write(0,*) 'Debug 1: ',ilx,iux
C
C Choose a pivot with median-of-three heuristics, leave it
C in the LPIV location
C
I = ILX
J = IUX
LPIV = (I+J)/2
PIV = X(LPIV)
IF (PIV.LT.X(I)) THEN
IT1 = X(I)
X(I) = X(LPIV)
X(LPIV) = IT1
PIV = X(LPIV)
ENDIF
IF (PIV.GT.X(J)) THEN
IT1 = X(J)
X(J) = X(LPIV)
X(LPIV) = IT1
PIV = X(LPIV)
ENDIF
IF (PIV.LT.X(I)) THEN
IT1 = X(I)
X(I) = X(LPIV)
X(LPIV) = IT1
PIV = X(LPIV)
ENDIF
C
C Now PIV is correct; place it into first location
IT1 = X(I)
X(I) = X(LPIV)
X(LPIV) = IT1
I = ILX - 1
J = IUX + 1
130 CONTINUE
I = I + 1
XK = X(I)
IF (XK.LT.PIV) GOTO 130
C
C Ensure finite termination for next loop
C
IT1 = XK
X(I) = PIV
140 CONTINUE
J = J - 1
XK = X(J)
IF (XK.GT.PIV) GOTO 140
X(I) = IT1
150 CONTINUE
IF (J.GT.I) THEN
IT1 = X(I)
X(I) = X(J)
X(J) = IT1
GO TO 130
END IF
if (i.eq.ilx) then
if (x(i).ne.piv) then
write(0,*) 'Should never ever get here????!!!!'
stop
endif
i = i + 1
endif
N1 = (I-1)-ILX+1
N2 = IUX-(I)+1
IF (N1.GT.N2) THEN
if (n1.gt.ithrs) then
ISTP = ISTP + 1
ISTACK(1,ISTP) = ILX
ISTACK(2,ISTP) = I-1
endif
if (n2.gt.ithrs) then
ISTP = ISTP + 1
ISTACK(1,ISTP) = I
ISTACK(2,ISTP) = IUX
endif
ELSE
if (n2.gt.ithrs) then
ISTP = ISTP + 1
ISTACK(1,ISTP) = I
ISTACK(2,ISTP) = IUX
endif
if (n1.gt.ithrs) then
ISTP = ISTP + 1
ISTACK(1,ISTP) = ILX
ISTACK(2,ISTP) = I-1
endif
ENDIF
ENDDO
ENDIF
DO J=N-1,1,-1
IF (X(J+1).LT.X(J)) THEN
XX = X(J)
I=J+1
100 CONTINUE
X(I-1) = X(I)
I = I+1
IF ((I.LE.N)) then
if (X(I).LT.XX) GOTO 100
endif
X(I-1) = XX
ENDIF
ENDDO
RETURN
END