dpnnzr.f
SUBROUTINE DPNNZR (I, XVAL, IPLACE, SX, IX, IRCX)
C***BEGIN PROLOGUE DPNNZR
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Warning: this routine is not intended to be user-callable.
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C***SUBSIDIARY
C***PURPOSE Subsidiary to DSPLP
C***LIBRARY SLATEC
C***TYPE DOUBLE PRECISION (PNNZRS-S, DPNNZR-D)
C***AUTHOR Hanson, R. J., (SNLA)
C Wisniewski, J. A., (SNLA)
C***DESCRIPTION
C
C DPNNZR LIMITS THE TYPE OF STORAGE TO A SEQUENTIAL SCHEME.
C SPARSE MATRIX NON ZERO RETRIEVAL SUBROUTINE.
C
C SUBROUTINE DPNNZR() GETS THE NEXT NONZERO VALUE IN ROW OR COLUMN
C +/- IRCX WITH AN INDEX GREATER THAN THE VALUE OF I.
C
C I ABSOLUTE VALUE OF THIS SUBSCRIPT IS TO BE EXCEEDED
C IN THE SEARCH FOR THE NEXT NONZERO VALUE. A NEGATIVE
C OR ZERO VALUE OF I CAUSES THE SEARCH TO START AT
C THE BEGINNING OF THE VECTOR. A POSITIVE VALUE
C OF I CAUSES THE SEARCH TO CONTINUE FROM THE LAST PLACE
C ACCESSED. ON OUTPUT, THE ARGUMENT I
C CONTAINS THE VALUE OF THE SUBSCRIPT FOUND. AN OUTPUT
C VALUE OF I EQUAL TO ZERO INDICATES THAT ALL COMPONENTS
C WITH AN INDEX GREATER THAN THE INPUT VALUE OF I ARE
C ZERO.
C XVAL VALUE OF THE NONZERO ELEMENT FOUND. ON OUTPUT,
C XVAL=0. WHENEVER I=0.
C IPLACE POINTER INFORMATION WHICH IS MAINTAINED BY THE PACKAGE.
C SX(*),IX(*) THE WORK ARRAYS WHICH ARE USED TO STORE THE SPARSE
C MATRIX. THESE ARRAY CONTENTS ARE AUTOMATICALLY
C MAINTAINED BY THE PACKAGE FOR THE USER.
C IRCX POINTS TO THE VECTOR OF THE MATRIX BEING SCANNED. A
C NEGATIVE VALUE OF IRCX INDICATES THAT ROW -IRCX IS TO BE
C SCANNED. A POSITIVE VALUE OF IRCX INDICATES THAT
C COLUMN IRCX IS TO BE SCANNED. A ZERO VALUE OF IRCX IS
C AN ERROR.
C
C THIS SUBROUTINE IS A MODIFICATION OF THE SUBROUTINE LNNZRS,
C SANDIA LABS. REPT. SAND78-0785.
C MODIFICATIONS BY K.L. HIEBERT AND R.J. HANSON
C REVISED 811130-1000
C REVISED YYMMDD-HHMM
C
C***SEE ALSO DSPLP
C***ROUTINES CALLED IDLOC, XERMSG
C***REVISION HISTORY (YYMMDD)
C 811215 DATE WRITTEN
C 890531 Changed all specific intrinsics to generic. (WRB)
C 890605 Removed unreferenced labels. (WRB)
C 890606 Changed references from IPLOC to IDLOC. (WRB)
C 891214 Prologue converted to Version 4.0 format. (BAB)
C 900315 CALLs to XERROR changed to CALLs to XERMSG. (THJ)
C 900328 Added TYPE section. (WRB)
C 910403 Updated AUTHOR and DESCRIPTION sections. (WRB)
C***END PROLOGUE DPNNZR