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235 lines
11 KiB
Fortran
235 lines
11 KiB
Fortran
C
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C Parallel Sparse BLAS v2.0
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C (C) Copyright 2006 Salvatore Filippone University of Rome Tor Vergata
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C Alfredo Buttari University of Rome Tor Vergata
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C
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C Redistribution and use in source and binary forms, with or without
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C modification, are permitted provided that the following conditions
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C are met:
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C 1. Redistributions of source code must retain the above copyright
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C notice, this list of conditions and the following disclaimer.
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C 2. Redistributions in binary form must reproduce the above copyright
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C notice, this list of conditions, and the following disclaimer in the
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C documentation and/or other materials provided with the distribution.
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C 3. The name of the PSBLAS group or the names of its contributors may
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C not be used to endorse or promote products derived from this
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C software without specific written permission.
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C
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C THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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C ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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C TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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C PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE PSBLAS GROUP OR ITS CONTRIBUTORS
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C BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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C CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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C SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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C INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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C CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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C ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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C POSSIBILITY OF SUCH DAMAGE.
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C
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C
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***********************************************************************
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* *
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* FUNCTION = This subroutine returns an array of pointers, L, *
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* to be used to sort the integer input vector K; *
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* the routine implements a list merge-sort *
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* *
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***********************************************************************
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* *
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* CALL MRGSRTD(N,K,L,IRET) *
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* *
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* INPUT = *
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* *
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* SYMBOLIC NAME: N *
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* POSITION: First parameter. *
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* ATTRIBUTES: INTEGER *
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* VALUES: >= 0 *
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* DESCRIPTION: Dimension of the array to be sorted *
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* *
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* SYMBOLIC NAME: K *
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* POSITION: Second parameter *
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* ATTRIBUTES: INTEGER ARRAY(N) *
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* VALUES: Any *
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* DESCRIPTION: Input array containing the keys, i.e., values *
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* to be sorted *
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* *
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* *
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* *
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* OUTPUT = *
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* *
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* SYMBOLIC NAME: L *
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* POSITION: Third parameter *
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* ATTRIBUTES: INTEGER ARRAY(N+2) *
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* VALUES: >= 0 *
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* DESCRIPTION: On exit, this array contains pointers to *
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* the keys array. *
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* *
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***********************************************************************
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***********************************************************************
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* *
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***********************************************************************
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***********************************************************************
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* ALGORITHM DESCRIPTION *
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* *
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* REFERENCES = (1) D. E. Knuth *
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* The Art of Computer Programming, *
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* vol.3: Sorting and Searching *
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* Addison-Wesley, 1973 *
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* *
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* FUNCTION = This subroutine is based on the well-known merge-sort *
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* algorithm; according to (1) we are sorting 'records' *
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* R(I) with respect to keys K(I), and to this purpose *
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* we use 'links' L(I); at the end of the subroutine, *
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* L(0) is the index of the first record in the sorted *
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* sequence, then for every record R(I), we have into *
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* L(I) the index of the next one in the sequence. A *
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* value L(I)=0 signals the end of the sequence. *
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* The sorting is stable, i.e., if K(I)=K(J) and I<J, *
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* then in the sorted sequence R(I) precedes R(J); many *
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* sorting algorithms, e.g. quicksort, are not stable. *
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* The list merge-sort is one of the fastest stable *
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* sortings available; it is guaranteed to run in *
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* O(N log N) time on both the average and worst cases. *
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* *
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* *
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***********************************************************************
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***********************************************************************
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* ALGORITHM EXAMPLE(S) *
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* *
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* EXAMPLE: Construct a sorted array of records RS from a vector R *
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* according to the keys stored in K *
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* *
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* CALL MRGSRTD(N,K,L,*100) *
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* I = L(0) *
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* DO 100 J = 1, N *
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* RS(J) = R(I) *
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* I = L(I) *
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* 100 CONTINUE ! RETURN POINT IF ARRAY ALREADY SORTED *
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* *
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* *
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* EXAMPLE: Sort in place array R *
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* *
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* CALL MRGSRTD(N,K,L,*400) *
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* LP = L(0) *
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* KK = 1 *
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* 100 CONTINUE *
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* IF ((LP.EQ.0).OR.(KK.GT.N)) GOTO 400 *
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* 200 CONTINUE *
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* IF (LP.GE.KK) GOTO 300 *
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* LP = L(LP) *
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* GOTO 200 *
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* 300 CONTINUE *
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* SWAP = R(KK) *
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* R(KK) = R(LP) *
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* R(LP) = SWAP *
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* LSWAP = L(LP) *
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* L(LP) = L(KK) *
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* L(KK) = LP *
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* LP = LSWAP *
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* KK = KK+1 *
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* GOTO 100 *
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* 400 CONTINUE *
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* *
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* *
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***********************************************************************
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SUBROUTINE MRGSRTD(N,K,L,IRET)
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C .. Scalar Arguments ..
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INTEGER N, IRET
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C ..
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C .. Array Arguments ..
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INTEGER K(N),L(0:N+1)
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C ..
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C .. Local Scalars ..
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INTEGER P,Q,S,T
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C ..
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C .. Intrinsic Functions ..
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INTRINSIC IABS,ISIGN
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C ..
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IRET = 0
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C First step: we are preparing ordered sublists, exploiting
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C what order was already in the input data; negative links
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C mark the end of the sublists
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L(0) = 1
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T = N + 1
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DO P = 1,N - 1
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IF (K(P).GE.K(P+1)) THEN
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L(P) = P + 1
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ELSE
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L(T) = - (P+1)
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T = P
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END IF
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END DO
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L(T) = 0
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L(N) = 0
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C See if the input was already sorted
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IF (L(N+1).EQ.0) THEN
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IRET = 1
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RETURN
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ELSE
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L(N+1) = IABS(L(N+1))
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END IF
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200 CONTINUE
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C Otherwise, begin a pass through the list.
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C Throughout all the subroutine we have:
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C P, Q: pointing to the sublists being merged
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C S: pointing to the most recently processed record
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C T: pointing to the end of previously completed sublist
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S = 0
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T = N + 1
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P = L(S)
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Q = L(T)
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IF (Q.EQ.0) RETURN
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300 CONTINUE
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IF (K(P).LT.K(Q)) GO TO 600
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400 CONTINUE
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L(S) = ISIGN(P,L(S))
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S = P
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P = L(P)
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IF (P.GT.0) GO TO 3100
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C Otherwise, one sublist ended, and we append to it the rest
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C of the other one.
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500 CONTINUE
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L(S) = Q
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S = T
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550 CONTINUE
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T = Q
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Q = L(Q)
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IF (Q.GT.0) GO TO 550
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GO TO 800
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600 CONTINUE
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L(S) = ISIGN(Q,L(S))
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S = Q
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Q = L(Q)
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IF (Q.GT.0) GO TO 3200
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700 CONTINUE
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L(S) = P
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S = T
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750 CONTINUE
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T = P
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P = L(P)
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IF (P.GT.0) GO TO 750
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800 CONTINUE
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P = -P
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Q = -Q
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IF (Q.EQ.0) THEN
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L(S) = ISIGN(P,L(S))
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L(T) = 0
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GO TO 200
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ELSE
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GO TO 300
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END IF
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3100 CONTINUE
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IF (K(P).LT.K(Q)) GO TO 600
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S = P
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P = L(P)
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IF (P.GT.0) GO TO 3100
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GO TO 500
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3200 CONTINUE
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IF (K(P).GE.K(Q)) GO TO 400
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S = Q
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Q = L(Q)
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IF (Q.GT.0) GO TO 3200
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GO TO 700
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END
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