SLATEC Routines --- PNNZRS ---

*DECK PNNZRS
      SUBROUTINE PNNZRS (I, XVAL, IPLACE, SX, IX, IRCX)
C***BEGIN PROLOGUE  PNNZRS
C***SUBSIDIARY
C***PURPOSE  Subsidiary to SPLP
C***LIBRARY   SLATEC
C***TYPE      SINGLE PRECISION (PNNZRS-S, DPNNZR-D)
C***AUTHOR  Hanson, R. J., (SNLA)
C           Wisniewski, J. A., (SNLA)
C***DESCRIPTION
C
C     PNNZRS LIMITS THE TYPE OF STORAGE TO A SEQUENTIAL SCHEME.
C     SPARSE MATRIX NON ZERO RETRIEVAL SUBROUTINE.
C
C     SUBROUTINE PNNZRS() 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  SPLP
C***ROUTINES CALLED  IPLOC, 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   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  PNNZRS