OpenMP on CRAN
Tim,
On 3/04/2020, at 2:01 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).
It has caused a lot of issues, it trips people on a daily basis which is just not worth it. Also with Apple's increasingly strict rules about what can be distributed we don't want to be in the business in maintaining a separate toolchain. There have been numerous issues with C++ exceptions so the fall out was much bigger than originally expected and it would only get worse.
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.
The idea is that if a package deems this critical, it can enable this for the users. As it is now, packages can still supply iomp and use it. That said, I would open for discussion the ability to distribute iomp with the R binary, but it would not be supported by R directly, i.e., it would be on the package author to make sure that the way the package operates is compatible with that binary. Let me know what you think.
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.
Yes, but OpenMP is rarely used for those tasks. In R OpenMP can be only used for very small subset of such tasks - which is why alternative approaches are much more common. Cheers, Simon
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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