OpenMP on CRAN
Hi, For what it's worth, it looks like it is still possible to use OpenMP on macOS with the system toolchain. Using the example file here: https://computing.llnl.gov/tutorials/openMP/samples/C/omp_hello.c I can compile + link + run this on macOS 10.15.4 and with: $ /usr/bin/clang -Xpreprocessor -fopenmp -I/usr/local/opt/libomp/include -L/usr/local/opt/libomp/lib -lomp omp_hello.c As for whether this is 'safe', or whether R could conceivably bundle and use its own copy of libomp is a separate question I cannot answer. But at least this is a mechanism for enterprising users to enable OpenMP in packages built from source if they so desire. Best, Kevin
On Thu, Apr 2, 2020 at 6:01 AM BATES Timothy <tim.bates at ed.ac.uk> wrote:
Moving to a compiler that drops support for OpenMP seems a sad choice, especially now we?ve all climbed the learning curve of the non-Apple compiler (the real barrier was lack of a pkg installer and that?s done now). Losing OpenMP for the CRAN version of OpenMx/umx (our SEM packages) would be a big loss for users (for whom the CRAN version now supports OpenMP giving them a 2-12x speed up). In general, R on Mac is made more viable by having OpenMP Re Brian?s points, I?d say that the distribution problem is crucial: Packages not on CRAN have dramatically diminished accessibility/useage. Second, a great range of compute-intensive problems are amenable to division amongst cores, including nearly all models that take more than a nominal amount of time to run: So simulations, CIs, bootstrapping, nearly everything in genetics all speeds up. I?d say especially on desktop/laptop. The big advantage of multi blade systems requires snowfall-type solutions, but desktops profit automatically from their multi-core structure and don;?t have multiple processors (except graphics, which no-one seems to be exploiting on CRAN-style R), so OpenMP is their one trick. I?d hope not to lose it. Best, t
On 2 Apr 2020, at 05:18, Prof Brian Ripley <ripley at stats.ox.ac.uk> wrote: On 01/04/2020 22:02, Simon Urbanek wrote:
JJB, 1. correct, there was too much trouble in this. But please feel free to start a new thread about this here if you have strong opinions.
Also note that it is possible (and not hard) to install packages from source with an OpenMP-supporting compiler, and how to do so is in the R-admin manual. The problems come in distributing them. The benefits of OpenMP are often overestimated, especially on desktop/laptop level hardware. But it is available for the small (tiny?) proportion of users who need it.
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