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84 lines
2.5 KiB
Fortran
84 lines
2.5 KiB
Fortran
*DECK SPPERM
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SUBROUTINE SPPERM (X, N, IPERM, IER)
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C***BEGIN PROLOGUE SPPERM
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C***PURPOSE Rearrange a given array according to a prescribed
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C permutation vector.
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C***LIBRARY SLATEC
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C***CATEGORY N8
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C***TYPE SINGLE PRECISION (SPPERM-S, DPPERM-D, IPPERM-I, HPPERM-H)
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C***KEYWORDS APPLICATION OF PERMUTATION TO DATA VECTOR
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C***AUTHOR McClain, M. A., (NIST)
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C Rhoads, G. S., (NBS)
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C***DESCRIPTION
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C
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C SPPERM rearranges the data vector X according to the
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C permutation IPERM: X(I) <--- X(IPERM(I)). IPERM could come
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C from one of the sorting routines IPSORT, SPSORT, DPSORT or
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C HPSORT.
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C
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C Description of Parameters
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C X - input/output -- real array of values to be rearranged.
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C N - input -- number of values in real array X.
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C IPERM - input -- permutation vector.
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C IER - output -- error indicator:
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C = 0 if no error,
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C = 1 if N is zero or negative,
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C = 2 if IPERM is not a valid permutation.
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C
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C***REFERENCES (NONE)
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C***ROUTINES CALLED XERMSG
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C***REVISION HISTORY (YYMMDD)
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C 901004 DATE WRITTEN
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C 920507 Modified by M. McClain to revise prologue text.
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C***END PROLOGUE SPPERM
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INTEGER N, IPERM(*), I, IER, INDX, INDX0, ISTRT
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REAL X(*), TEMP
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C***FIRST EXECUTABLE STATEMENT SPPERM
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IER=0
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IF(N.LT.1)THEN
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IER=1
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CALL XERMSG ('SLATEC', 'SPPERM',
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+ 'The number of values to be rearranged, N, is not positive.',
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+ IER, 1)
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RETURN
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ENDIF
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C
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C CHECK WHETHER IPERM IS A VALID PERMUTATION
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C
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DO 100 I=1,N
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INDX=ABS(IPERM(I))
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IF((INDX.GE.1).AND.(INDX.LE.N))THEN
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IF(IPERM(INDX).GT.0)THEN
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IPERM(INDX)=-IPERM(INDX)
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GOTO 100
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ENDIF
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ENDIF
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IER=2
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CALL XERMSG ('SLATEC', 'SPPERM',
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+ 'The permutation vector, IPERM, is not valid.', IER, 1)
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RETURN
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100 CONTINUE
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C
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C REARRANGE THE VALUES OF X
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C
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C USE THE IPERM VECTOR AS A FLAG.
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C IF IPERM(I) > 0, THEN THE I-TH VALUE IS IN CORRECT LOCATION
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C
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DO 330 ISTRT = 1 , N
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IF (IPERM(ISTRT) .GT. 0) GOTO 330
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INDX = ISTRT
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INDX0 = INDX
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TEMP = X(ISTRT)
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320 CONTINUE
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IF (IPERM(INDX) .GE. 0) GOTO 325
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X(INDX) = X(-IPERM(INDX))
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INDX0 = INDX
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IPERM(INDX) = -IPERM(INDX)
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INDX = IPERM(INDX)
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GOTO 320
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325 CONTINUE
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X(INDX0) = TEMP
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330 CONTINUE
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C
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RETURN
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END
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