Index: /issm/trunk-jpl/src/m/math/cfl_step.m
===================================================================
--- /issm/trunk-jpl/src/m/math/cfl_step.m	(revision 12998)
+++ /issm/trunk-jpl/src/m/math/cfl_step.m	(revision 12998)
@@ -0,0 +1,23 @@
+function maxtime=cfl_step(md,vx,vy);
+%CFL_STEP - return the maximum time step for the model in years
+%
+%   Dt < 0.5 / ( u/Dx +v/Dy )
+%
+%   Usage:
+%      maxtime=cfl_step(md,vx,vy);
+%
+%   Example:
+%      dt=cfl_step(md,md.results.DiagnosticSolution.Vx,md.results.DiagnosticSolution.Vy)
+
+%Check length of velocities 
+if size(vx,1)~=md.mesh.numberofvertices & size(vy,1)~=md.mesh.numberofvertices,
+	error('timestpes error message: size of velocity components must be the same as md.mesh.numberofvertices');
+end
+
+index=md.mesh.elements;
+edgex=max(md.mesh.x(index),[],2)-min(md.mesh.x(index),[],2);
+edgey=max(md.mesh.y(index),[],2)-min(md.mesh.y(index),[],2);
+vx=max(abs(vx(index)),[],2);
+vy=max(abs(vy(index)),[],2);
+
+maxtime=1/2*min(1./(vx./edgex+vy./edgey));