dpchng.f
SUBROUTINE DPCHNG (II, XVAL, IPLACE, SX, IX, IRCX)
C***BEGIN PROLOGUE DPCHNG
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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 (PCHNGS-S, DPCHNG-D)
C***AUTHOR Hanson, R. J., (SNLA)
C Wisniewski, J. A., (SNLA)
C***DESCRIPTION
C
C SUBROUTINE DPCHNG CHANGES ELEMENT II IN VECTOR +/- IRCX TO THE
C VALUE XVAL.
C DPCHNG LIMITS THE TYPE OF STORAGE TO A SEQUENTIAL SCHEME.
C SPARSE MATRIX ELEMENT ALTERATION SUBROUTINE.
C
C II THE ABSOLUTE VALUE OF THIS INTEGER IS THE SUBSCRIPT FOR
C THE ELEMENT TO BE CHANGED.
C XVAL NEW VALUE OF THE MATRIX ELEMENT BEING CHANGED.
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 ARRAYS ARE AUTOMATICALLY MAINTAINED BY THE
C PACKAGE FOR THE USER.
C IRCX POINTS TO THE VECTOR OF THE MATRIX BEING UPDATED.
C A NEGATIVE VALUE OF IRCX INDICATES THAT ROW -IRCX IS
C BEING UPDATED. A POSITIVE VALUE OF IRCX INDICATES THAT
C COLUMN IRCX IS BEING UPDATED. A ZERO VALUE OF IRCX IS
C AN ERROR.
C
C SINCE DATA ITEMS ARE KEPT SORTED IN THE SEQUENTIAL DATA STRUCTURE,
C CHANGING A MATRIX ELEMENT CAN REQUIRE THE MOVEMENT OF ALL THE DATA
C ITEMS IN THE MATRIX. FOR THIS REASON, IT IS SUGGESTED THAT DATA
C ITEMS BE ADDED A COL. AT A TIME, IN ASCENDING COL. SEQUENCE.
C FURTHERMORE, SINCE DELETING ITEMS FROM THE DATA STRUCTURE MAY ALSO
C REQUIRE MOVING LARGE AMOUNTS OF DATA, ZERO ELEMENTS ARE EXPLICITLY
C STORED IN THE MATRIX.
C
C THIS SUBROUTINE IS A MODIFICATION OF THE SUBROUTINE LCHNGS,
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 DPRWPG, IDLOC, XERMSG
C***REVISION HISTORY (YYMMDD)
C 811215 DATE WRITTEN
C 890531 Changed all specific intrinsics to generic. (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 DPCHNG