[n,b,x,nelt,ia,ja,a,isym,rwork,iwork]=dsdi(n,b,x,nelt,ia,ja,a,isym,rwork,iwork);

function [n,b,x,nelt,ia,ja,a,isym,rwork,iwork]=dsdi(n,b,x,nelt,ia,ja,a,isym,rwork,iwork);
%***BEGIN PROLOGUE  DSDI
%***PURPOSE  Diagonal Matrix Vector Multiply.
%            Routine to calculate the product  X = DIAG*B, where DIAG
%            is a diagonal matrix.
%***LIBRARY   SLATEC (SLAP)
%***CATEGORY  D1B4
%***TYPE      doubleprecision (SSDI-S, DSDI-D)
%***KEYWORDS  ITERATIVE PRECONDITION, LINEAR SYSTEM SOLVE, SLAP, SPARSE
%***AUTHOR  Greenbaum, Anne, (Courant Institute)
%           Seager, Mark K., (LLNL)
%             Lawrence Livermore National Laboratory
%             PO BOX 808, L-60
%             Livermore, CA 94550 [phone]
%             [e-mail]
%***DESCRIPTION
%
% *Usage:
%     INTEGER  N, NELT, IA(NELT), JA(NELT), ISYM, IWORK(10)
%     doubleprecision B(N), X(N), A(NELT), RWORK(USER DEFINED)
%
%     CALL DSDI (N, B, X, NELT, IA, JA, A, ISYM, RWORK, IWORK)
%
% *Arguments:
% N      :IN       Integer
%         Order of the Matrix.
% B      :IN       doubleprecision B(N).
%         Vector to multiply the diagonal by.
% X      :OUT      doubleprecision X(N).
%         Result of DIAG*B.
% NELT   :DUMMY    Integer.
% IA     :DUMMY    Integer IA(NELT).
% JA     :DUMMY    Integer JA(NELT).
% A      :DUMMY    doubleprecision A(NELT).
% ISYM   :DUMMY    Integer.
%         These are for compatibility with SLAP MSOLVE calling sequence.
% RWORK  :IN       doubleprecision RWORK(USER DEFINED).
%         Work array holding the diagonal of some matrix to scale
%         B by.  This array must be set by the user or by a call
%         to the SLAP routine DSDS or DSD2S.  The length of RWORK
%         must be >= IWORK(4)+N.
% IWORK  :IN       Integer IWORK(10).
%         IWORK(4) holds the offset into RWORK for the diagonal matrix
%         to scale B by.  This is usually set up by the SLAP pre-
%         conditioner setup routines DSDS or DSD2S.
%
% *Description:
%         This routine is supplied with the SLAP package to perform
%         the  MSOLVE  operation for iterative drivers that require
%         diagonal  Scaling  (e.g., DSDCG, DSDBCG).   It  conforms
%         to the SLAP MSOLVE CALLING CONVENTION  and hence does not
%         require an interface routine as do some of the other pre-
%         conditioners supplied with SLAP.
%
%***SEE ALSO  DSDS, DSD2S
%***REFERENCES  (NONE)
%***ROUTINES CALLED  (NONE)
%***REVISION HISTORY  (YYMMDD)
%   871119  DATE WRITTEN
%   881213  Previous REVISION DATE
%   890915  Made changes requested at July 1989 CML Meeting.  (MKS)
%   890922  Numerous changes to prologue to make closer to SLATEC
%           standard.  (FNF)
%   890929  Numerous changes to reduce SP/DP differences.  (FNF)
%   910411  Prologue converted to Version 4.0 format.  (BAB)
%   920511  Added complete declaration section.  (WRB)
%   930701  Updated CATEGORY section.  (FNF, WRB)
%***end PROLOGUE  DSDI
%     .. Scalar Arguments ..
%     .. Array Arguments ..
persistent i locd ; 

rwork_shape=size(rwork);rwork=reshape(rwork,1,[]);
%     .. Local Scalars ..
if isempty(i), i=0; end;
if isempty(locd), locd=0; end;
%***FIRST EXECUTABLE STATEMENT  DSDI
%
%         Determine where the inverse of the diagonal
%         is in the work array and then scale by it.
%
locd = fix(iwork(4) - 1);
for i = 1 : n;
x(i) = rwork(locd+i).*b(i);
end; i = fix(n+1);
%------------- LAST LINE OF DSDI FOLLOWS ----------------------------
rwork_shape=zeros(rwork_shape);rwork_shape(:)=rwork(1:numel(rwork_shape));rwork=rwork_shape;
end
%DECK DSDOMN