| Elephant Man <conanospamic@gmail.com>: Jan 25 08:47AM Article d'annulation émis par un modérateur JNTP via Nemo. |
| Horizon68 <horizon@horizon.com>: Jan 24 03:57PM -0800 Hello... My efficient Threadpool engine with priorities that scales very well was updated to version 3.7 ParallelFor() now supports grainsize, please read the following about grainsize: procedure ParallelFor(nMin, nMax:integer;aProc: TParallelProc;GrainSize:integer=1;Ptr:pointer=nil;pmode:TParallelMode=pmBlocking;Priority:TPriorities=NORMAL_PRIORITY); nMin and nMax parameters of the ParallelFor() are the minimum and maximum integer values of the variable of the ParallelFor() loop, aProc parameter of ParallelFor() is the procedure to call, and GrainSize integer parameter of ParallelFor() is the following: The grainsize sets a minimum threshold for parallelization. A rule of thumb is that grainsize iterations should take at least 100,000 clock cycles to execute. For example, if a single iteration takes 100 clocks, then the grainsize needs to be at least 1000 iterations. When in doubt, do the following experiment: 1- Set the grainsize parameter higher than necessary. The grainsize is specified in units of loop iterations. If you have no idea of how many clock cycles an iteration might take, start with grainsize=100,000. The rationale is that each iteration normally requires at least one clock per iteration. In most cases, step 3 will guide you to a much smaller value. 2- Run your algorithm. 3- Iteratively halve the grainsize parameter and see how much the algorithm slows down or speeds up as the value decreases. A drawback of setting a grainsize too high is that it can reduce parallelism. For example, if the grainsize is 1000 and the loop has 2000 iterations, the ParallelFor() method distributes the loop across only two processors, even if more are available. And you can pass a parameter in Ptr as pointer to ParallelFor(), and you can set pmode parameter of to pmBlocking so that ParallelFor() is blocking or to pmNonBlocking so that ParallelFor() is non-blocking, and the Priority parameter is the priority of ParallelFor(). Look inside the test.pas example to see how to use it. You can download it from: https://sites.google.com/site/scalable68/an-efficient-threadpool-engine-with-priorities-that-scales-very-well Thank you, Amine Moulay Ramdane. |
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