PROCEDURE mtt_update(VAR xnew : StateVector;
dx,x,AAx : StateVector;
VAR AA : StateMatrix;
DT : REAL;
STEPFACTOR : INTEGER;
Nx : INTEGER;
METHOD : IntegrationMethod);
{
###############################################################
## Version control history
###############################################################
## $Id$
## $Log$
## Revision 1.4 1998/08/14 10:54:58 peterg
## Use sparse computation where possible
##
###############################################################
}
CONST
Small = 0.000001;
VAR
i,j : INTEGER;
BB : StateVector;
DDT : REAL;
(*$I mtt_solve.p *)
(*$I mtt_sparse.p *)
BEGIN{mtt_update}
IF Method=1 THEN {Euler}
BEGIN{Euler}
DDT := DT/STEPFACTOR;
FOR i := 1 TO Nx DO
xnew[i] := xnew[i] + dx[i]*DDT;
END {Euler}
ELSE IF (Method=2) OR (METHOD=3) OR (METHOD=4) THEN {Implicit}
BEGIN {Implicit methods}
FOR i := 1 TO Nx DO {BB is (1-A*dt)*x +dx*dt}
BB[i] := AAx[i] + DT*dx[i];
{Solve the equation AAx = B}
IF (Method=2) OR (METHOD=3) THEN {Use SVD}
mtt_solve(xnew,AA,BB,Nx,Small)
ELSE {Sparse CG solution}
mtt_sparse(BB,Nx,STEPFACTOR,xnew);
END{Implicit methods}
ELSE
Writeln("Method >4 is not defined");
END{mtt_update};