Question about Compiling, external functions, and For loops

*To*: mathgroup at smc.vnet.net*Subject*: [mg56500] Question about Compiling, external functions, and For loops*From*: Ravi Balasubramanian <ravib at andrew.cmu.edu>*Date*: Tue, 26 Apr 2005 21:53:38 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Hi Math Group-ers, [Contact the author to get the notebook attachment mentioned below - moderator] I think I have a pretty standard problem, but I was unable to find a solution either in the help pages or in Mathgroup; apologies if the answer is already online; I will really appreciate it if you can direct me to it. My code is attached in an nb file. I have a function findCost2, created as a module, that must be called many times in a for-loop. Since I have to call it so many times, I want to compile the whole for-loop. Here are the specifics: findCost2 is an interpolation function: given a two-d matrix of costs, and a new state, it finds the cost of the new state by interpolating the nearby values. I pass findCost2 the matrix of costs, the list of states (given in two 1-d arrays, viz., thetaTable and thetapTable), and the new state; it returns a cost value. compiledLoop is a compiled module that calls findCost2 many times, while uncompiledLoop is an uncompiled module that calls findCost2 many times. Here is a comparison of the two speeds. compiledLoop Time: 134.734 Second uncompiledLoop Time: 136. Second I notice that there is not much gain in compiling, probably because of the external calls to findCost2; but I would really prefer not include the code in findCost2 into the loop. This seems to be a standard question in the Mathgroup archives; is there a solution? Any suggestions? Help greatly appreciated. Ravi Balasubramanian The Robotics Institute, Carnegie Mellon University