Search found 805 matches

by MarkB
Mon Dec 21, 2020 2:07 am
Forum: Using OpenMP
Topic: macOS Big Sur
Replies: 2
Views: 268

Re: macOS Big Sur

OpenMP has no control over vendor's releases, so I'm afraid this is entirely down to Apple!

As far as I know the situation for Big Sur has not changed from other recent MacOS versions - you need a separate compiler install to support OpenMP.
by MarkB
Mon Nov 30, 2020 1:01 pm
Forum: Using OpenMP
Topic: Collapse not working
Replies: 3
Views: 429

Re: Collapse not working

I presume that the 1-thread performance of the collapsed version is also bad? It's quite rare, but I do see this kind of thing once in a while - the OpenMP directives cause the compiler optimisation to fail in some way. In this case it might be the address computations that are the problem. Sometime...
by MarkB
Tue Aug 11, 2020 8:31 am
Forum: Using OpenMP
Topic: Tasks executed by thread 0 only
Replies: 2
Views: 2812

Re: Tasks executed by thread 0 only

There is no way to specify which thread executes a task. Most likely you do not need to restrict file I/O to thread 0, as long as you don't have multiple tasks/threads trying to write the same file concurrently. But a pattern like this might work for you: #pragma omp parallel { #pragma omp master { ...
by MarkB
Fri Jul 24, 2020 1:51 pm
Forum: Using OpenMP
Topic: loop
Replies: 1
Views: 1374

Re: loop

Where is normal_fact modified? (Your code snippet doesn't show this).
by MarkB
Thu Jun 18, 2020 2:41 am
Forum: Using OpenMP
Topic: OPENMP Performance Problem
Replies: 3
Views: 1081

Re: OPENMP Performance Problem

The OpenMP runtime will create threads even though the parallel region does nothing, and these may well stay alive and consume CPU resources outside of the parallel regions. What could be happening is that the threads are being bound to the same core as the MPI process. You may need to set some flag...
by MarkB
Tue Jun 16, 2020 5:53 am
Forum: Using OpenMP
Topic: parallel http requests program
Replies: 1
Views: 693

Re: parallel http requests program

This is a rather unusual use case for OpenMP - normally it is used for compute intensive tasks. I think the performance of this code will be be very dependent on your I/O and network bandwidth.
by MarkB
Tue Jun 16, 2020 5:46 am
Forum: Using OpenMP
Topic: OPENMP Performance Problem
Replies: 3
Views: 1081

Re: OPENMP Performance Problem

What are you using to measure the execution time?
by MarkB
Mon Jun 08, 2020 4:05 am
Forum: Using OpenMP
Topic: Parallel DO hangs 2nd time thru
Replies: 1
Views: 690

Re: Parallel DO hangs 2nd time thru

I would not be surprised if the (version of the) Intel compiler does not support mixing C++ threads and OpenMP in the same application in this way.
by MarkB
Mon May 25, 2020 6:46 am
Forum: Using OpenMP
Topic: Issue with CPU affinity in teams in OpenMP 5.0
Replies: 1
Views: 827

Re: Issue with CPU affinity in teams in OpenMP 5.0

In OpenMP 5.0, binding of (the initial thread of) teams to places (i.e. sockets, cores. hardware threads) is left up to the implementation - see lines 29-31 on page 83. I'm not aware of any compiler-specific support for this in gcc. Is using nested parallel regions not a possible solution for your u...
by MarkB
Tue May 19, 2020 3:06 am
Forum: Using OpenMP
Topic: How to parallelize a recursive function
Replies: 8
Views: 2267

Re: How to parallelize a recursive function

But other threads’ job is directly depended on this thread. They will never touch “return true” statement (can’t complete assigning values to all grids of matrix) if that thread doesn’t return and revise its value. In this way, the code gets stuck in a dead-end. Sorry, I don't really understand - "...