ParallelMap inefficient?

*To*: mathgroup at smc.vnet.net*Subject*: [mg27290] ParallelMap inefficient?*From*: Mike Yukish <may106 at psu.edu>*Date*: Fri, 16 Feb 2001 03:58:54 -0500 (EST)*Organization*: Penn State University, Center for Academic Computing*Sender*: owner-wri-mathgroup at wolfram.com

Hello, I am starting to use the parallel programming toolbox, and I've found the ParallelMap[ ] function to be essentially broken, most likely due to some sort of comm glitch. I was curious if anyone else has experienced a similar problem, or if it is just my network. If I run the following commands (listtt is a 5 element list of real numbers), with one remote server active... x1=SessionTime[]; ParallelMap[Sin,listtt] SessionTime[]-x1 It takes 5-7 seconds. This is to connect with a slave computer that is sharing a hub with the master. Obviously something is wrong. By contrast, if I define the function on the slave maparoni[x_]:=Map[Sin,x] and do the following... Do[ With[{x=listtt},RemoteEvaluate[maparoni[x]] ] , {20} ] SessionTime[]-x1 It only takes 5 seconds. Note the difference. I am executing the Sin[ ] function twenty times more, I am passing discrete hunks of data twenty times more, and I am passing twenty times the total amount of data, yet it takes less time to complete. So the basic linking between computers appears to work OK. Anybody else have experience with the ParallelMap[ ] function? I see similar performance with ParallelTable[ ]