Index: mttroot/mtt/bin/trans/p/mtt_update.p
==================================================================
--- mttroot/mtt/bin/trans/p/mtt_update.p
+++ mttroot/mtt/bin/trans/p/mtt_update.p
@@ -1,48 +1,55 @@
-PROCEDURE mtt_update(VAR xnew	: StateVector;
-			 dx,x	: StateVector;
-			 DT	: REAL;
-			 Nx	: INTEGER;
-			 METHOD	: IntegrationMethod;
-			 AA	: StateMatrix );
+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,Ax : StateVector;
-   rsq	 : REAL;
+   i,j : INTEGER;
+   BB  : StateVector;
+   DDT : REAL;
    
 (*$I mtt_solve.p *)
 (*$I mtt_sparse.p *)
    
 BEGIN{mtt_update}
+   
    IF Method=1 THEN {Euler}
-      FOR i := 1 TO  Nx DO
-	 xnew[i] := xnew[i] + dx[i]*DT
-	 
-      ELSE IF (Method=2) OR (METHOD=3) OR (METHOD=4) THEN {Implicit}
+   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}
-	 mtt_asub(x,Ax,Nx); {Sparse computation of (1-A*dt)*x}
+	 
 	 FOR i := 1 TO  Nx DO {BB is (1-A*dt)*x +dx*dt}
-	    BB[i] := Ax[i]+ DT*dx[i];
+	    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,xnew,rsq);
+	    mtt_sparse(BB,Nx,STEPFACTOR,xnew);
       END{Implicit methods}
       ELSE
 	 Writeln("Method >4 is not defined");
    
 END{mtt_update};