Low efficiency of uw.fn.evaluate comparing with the uw.fn.evalf in swarm.advection

[NengLu]

Here is the case1 with free surface boundary condition from Crameri2012. The swarm particle number is 256 * 64 * 9 = 147456.

In swarm advection, the uw.fn.evaif works for evaluating the velocity field while the uw.fn.evaluate doesn't.

The fn.evaluate may need to be improved.

Ex_Crameri2012Case1_testSwarmAdvection.txt