I am trying to speed up an algorithm using futures, but I am getting some unexpected results (and no real speed improvements), and I was wondering if someone more experienced could have a look a the code and tell me what am I doing wrong.
I put up the code in this repository: https://github.com/alex-hhh/cp3-exeriments, unfortunately it is the simplest meaningful example that I can come up with. Most of the functions, however are just support functions and there are six implementation of the same algorithm. Basically, the problem I am trying to solve is to fit a model to existing data and this is done by evaluating 2.5 million combinations of parameters. My best, non-futures based, algorithm can do this in about 3 seconds (8 seconds in DrRacket). Given that each of this 2.5 million combination is completely independent from the others, they could all be done in parallel. Given this, I "sliced" the combinations into 30 groups and tried to perform each "slice" in its own future and select the best among the 30 results produced by these futures. Unfortunately, while the futures versions of the algorithm produce the correct result, the algorithm runs at the same speed as the non-futures version. My `processor-count` returns 8, so I would expect at least some level of parallelism. As a first step, I tried using `would-be-future`, to see if it reported any operations which might block, but nothing was printed out. I also tried using the futures visualized, and I found the following: * the code appears to be blocking on primitive operations, such as +, -, < etc. * I suspect these operations are inside the code generated by the `for` loops, so I am not sure how to remove them without making the code even more difficult to read. * there seems to be a lot more time spent in the garbage collector when running the futures visualizer than without it (DrRacket runs with unlimited memory) So I am wondering if someone who is more familiar with futures can look at the code and provide some hints about what can be done to make this code run in parallel (or if it cannot, I would like to understand why). This is already a long message, so I will not add further details here, but the repository at https://github.com/alex-hhh/cp3-exeriments has an explanation of what every function does, and I am happy to provide further clarifications if needed. Thanks, Alex. -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/8bf6f7c4-3b2f-4b86-9a8a-be68e82d09cfo%40googlegroups.com.
