That doesnt look like it has anything to do with omp On Mon, Jun 24, 2019 at 6:40 PM kellen sunderland < [email protected]> wrote:
> I remember this hang as well, it was pretty hard to reproduce IIRC. I > believe the stacks for the hang are here: > https://gist.github.com/KellenSunderland/893d11165e19d1efcf5c0fe8e8584600 > and > the trick was we could only debug it up to the point that we hit: > > #0 0x00007fec6df1ba4f in futex_wait (private=0, expected=1, > futex_word=0x7fec60843758) > at ../sysdeps/unix/sysv/linux/futex-internal.h:61 > #1 futex_wait_simple (private=0, expected=1, futex_word=0x7fec60843758) > at ../sysdeps/nptl/futex-internal.h:135 > #2 __pthread_once_slow (once_control=0x7fec60843758, > init_routine=0x7fec605f38f0) > at pthread_once.c:105 > ... > #6 0x00007fec6061c577 in cudaSetDevice () from > /usr/local/cuda/lib64/libcudart.so.9.0 > > because the code in libcudart is obviously closed source we couldn't dig > into what threading work was going on when we called cudaSetDevice. > > On Mon, Jun 24, 2019 at 6:13 PM Pedro Larroy <[email protected] > > > wrote: > > > If you check initialize.cc we seem to be explicitly disabling that > > behaviour in pthread_at_fork which seems to cause thread contention > > during multiprocessing. Why do we need this major advantage for the > > library if that's the case? > > > > Related PRs: > > > > https://github.com/apache/incubator-mxnet/pull/10820 > > https://github.com/apache/incubator-mxnet/issues/14396 > > > > The original code was authored in this PR: > > > > https://github.com/apache/incubator-mxnet/pull/8677 > > > > I actually remember this fix, it was done during a release as the cuda > > runtime was forking and the engine was being re-entered. If that > > situation is now happening anymore it might not be needed any longer. > > I don't think we know the cause why there was a fork inside cuda, so > > the code has grown around a fix for an issue which its root cause was > > not understood, and side effects which this fix caused afterwards. > > > > My build uses MKL+LLVM OMP+DEBUG as seen in the container provided in > > the link above, no libgomp. > > > > I didn't try the Make build. > > > > I would refactor the code linked above and stop using pthread_at_fork, > > since OMP assumes it won't be initialized twice, but needs to be very > > well tested to make sure it doesn't cause bugs or affect the fixes > > done on the linked PRs above. > > > > Pedro. > > > > On Mon, Jun 24, 2019 at 5:38 PM Chris Olivier <[email protected]> > > wrote: > > > > > > one major advantage of intel/llvm omp is that it spawns a new thread > pool > > > after fork if a thread pool was already created. this is so that omp > can > > be > > > used in the forked processes. libgomp doesn’t do this so it’ll just > lock > > up > > > if you try to do omp in the forked process. > > > > > > is your build linking libgomp as well? > > > > > > standard mkl build (from Makefile) uses same omp library. are there > > > problems with that build? > > > > > > what changes need to be made to make the assertion not fire? > > > > > > On Mon, Jun 24, 2019 at 5:32 PM Pedro Larroy < > > [email protected]> > > > wrote: > > > > > > > There's an assertion which is easily reproducible, and also there's a > > > > crash including core dump, the latter is not easy to reproduce for me > > > > in different environments. I have also seen mxnet getting stuck > > > > without progressing with this build configuration and using no CPU at > > > > all when running unit tests. > > > > > > > > In my view, the root cause of the assertion is that we are > re-entering > > > > OMP initialization when spawning threads on the following code > through > > > > pthread_at_fork > > > > > > > > > > > https://github.com/apache/incubator-mxnet/blob/master/src/initialize.cc#L58 > > > > > > > > This causes double initialization of the OMP engine, including the > > > > assertion which you are asking about, and I suspect some additional > > > > overhead. That's the shady forking part you are asking for. > > > > > > > > A question for you: What is the cause of runtime differences between > > > > OMP runtimes? Shouldn't the implementation overhead diminish as > > > > threads run longer? > > > > > > > > Pedro. > > > > > > > > On Mon, Jun 24, 2019 at 5:10 PM Chris Olivier <[email protected] > > > > > > wrote: > > > > > > > > > > What’s the reason for the assertion failure? btw classifying an > > assertion > > > > > failure a “crash” is debatable. As I stated in the original issue a > > long > > > > > time ago, it’s possible something shady is being done with when > > forking > > > > > that should be fixed. The assertion should be root caused. > > > > > > > > > > > > > > > > > > > > On Mon, Jun 24, 2019 at 1:22 PM Pedro Larroy < > > > > [email protected]> > > > > > wrote: > > > > > > > > > > > Added a dockerfile, and reports of a crash in my local machine > when > > > > > > running MKL+OMP+DEBUG, with Anton's branch the crash happened as > > well. > > > > > > I couldn't reproduce the crash on my EC2 machine: > > > > > > Added the backtrace of the crash as well. > > > > > > > > > > > > https://github.com/apache/incubator-mxnet/issues/10856 > > > > > > > > > > > > Dockerfile here: > > > > > > > > > > > > https://github.com/larroy/mxnet_omp > > > > > > > > > > > > Kind regards. > > > > > > > > > > > > Pedro. > > > > > > > > > > > > On Thu, Jun 20, 2019 at 5:29 PM Marco de Abreu < > > > > [email protected]> > > > > > > wrote: > > > > > > > > > > > > > > As already proposed, I think the easiest way to get a common > > > > > > understanding > > > > > > > is if we start with a few docker containers. Pedro, would it be > > > > possible > > > > > > > for you to wrap your benchmarks into a few containers that will > > > > produce > > > > > > > your shown results? That way, we can avoid possible > > > > misunderstandings and > > > > > > > also pinpoint the exact parts where people disagree or > > misunderstood > > > > each > > > > > > > other. > > > > > > > > > > > > > > -Marco > > > > > > > > > > > > > > Pedro Larroy <[email protected]> schrieb am Do., > 20. > > Juni > > > > > > 2019, > > > > > > > 21:47: > > > > > > > > > > > > > > > I can confirm that we are linking with two versions of omp, > I'm > > > > > > > > gaining more clarity into this topic, but I have still > > questions, > > > > the > > > > > > > > facts that I got so far are the folllowing: > > > > > > > > > > > > > > > > * #1: We are linking with two versions of omp, intel's omp > and > > llvm > > > > > > > > openmp when building with MKL enabled. > > > > > > > > * #2: We have 3 different possible OMP versions: Intel OMP > > (comes > > > > with > > > > > > > > MKL), LLVM OpenMP (3rdparty/openmp), libgomp (comes with gcc) > > (This > > > > > > > > one is used on the PR proposed by Anton). > > > > > > > > > > > > > > > > Questions: > > > > > > > > > > > > > > > > * #1 Is it ok to have two versions of openmp linked at the > > same > > > > time? > > > > > > > > * #2 Which implementation of OMP gives the best performance? > > (See > > > > > > > > total training time of my measurement for a partial answer) > > > > > > > > * #3 Should we have a build flag so we can choose the OMP > > version > > > > at > > > > > > > > runtime? > > > > > > > > * #4 Which Compiler and build flags did Chris use to get 10x > > > > slowdown? > > > > > > > > * #5 @Stas: is there a script to replicate your benchmarks > > > > easily? If > > > > > > > > so could you provide a link? I think we would need to > > reproduce > > > > your > > > > > > > > benchmarks and verify which versions are being linked. It's > > > > possible > > > > > > > > that while compiling with MKL intel's omp was pulled in > > instead of > > > > > > > > GNU OpenMP. > > > > > > > > * #6 @Chris: how to maintain the copy of LLVM's Openmp? > > Should we > > > > > > > > update the subrepo regularly? > > > > > > > > > > > > > > > > My conclusion so far: > > > > > > > > > > > > > > > > * #1 We should avoid linking two versions of omp if possible > > and > > > > > > > > allow users to choose one in the build as we do for BLAS. > > > > > > > > * #2 For performance reasons and more control vs different > > > > compiler > > > > > > > > versions seems it makes indeed sense to keep the LLVM OpenMP > > > > version > > > > > > > > in 3rdparty for now. So unless some more data is gathered, it > > makes > > > > > > > > sense not to remove it as of now. > > > > > > > > * #3 We should provide build options to choose which openmp > > > > library > > > > > > > > is to be used from the three options available, including > > libgomp. > > > > > > > > * #4 Refining the build we could also enable OpenMP in mac > > without > > > > > > > > additional contortions (doesn't work as of today): > > > > > > > > https://iscinumpy.gitlab.io/post/omp-on-high-sierra/ > > > > > > > > * #5 We should add different omp versions to our benchmarks > > and > > > > track > > > > > > > > the performance, so this data is available for prescribing > the > > best > > > > > > > > build options and for binary releases. > > > > > > > > > > > > > > > > This is also an interesting related gh issue posted in the > > mkl-dnn > > > > > > > > repository: https://github.com/intel/mkl-dnn/issues/230 > > > > > > > > > > > > > > > > > > > > > > > > I don't observe the order of magnitude divergence reported by > > > > Chris in > > > > > > > > vanilla Ubuntu 18.04 in samples / s but the full training > > finishes > > > > > > > > indeed faster with the OMP from 3rdparty (LLVM openmp) vs > > libgomp. > > > > > > > > > > > > > > > > There's also differences in training time when using MKL and > > the , > > > > > > > > it's actually a bit slower, I don't know if it's related to > > OMP. > > > > > > > > > > > > > > > > gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1) > > > > > > > > > > > > > > > > Anton's branch: [email protected]:lebeg/incubator-mxnet.git > > branch > > > > > > 'omp' > > > > > > > > (py3_venv) piotr@ec2 cpu:0: ~/mxnet_openmp [omp]> ldd > > > > > > > > build/libmxnet.so |grep -i omp > > > > > > > > libgomp.so.1 => > /usr/lib/x86_64-linux-gnu/libgomp.so.1 > > > > > > > > (0x00007fd99a51d000) > > > > > > > > > > > > > > > > time python train_mnist.py > > > > > > > > > > > > > > > > INFO:root:Epoch[18] Validation-accuracy=0.984176 > > > > > > > > INFO:root:Epoch[19] Batch [0-100] Speed: 41617.00 > > samples/sec > > > > > > > > accuracy=1.000000 > > > > > > > > INFO:root:Epoch[19] Batch [100-200] Speed: 47990.69 > > samples/sec > > > > > > > > accuracy=0.999531 > > > > > > > > INFO:root:Epoch[19] Batch [200-300] Speed: 47517.01 > > samples/sec > > > > > > > > accuracy=0.999687 > > > > > > > > INFO:root:Epoch[19] Batch [300-400] Speed: 47430.53 > > samples/sec > > > > > > > > accuracy=1.000000 > > > > > > > > INFO:root:Epoch[19] Batch [400-500] Speed: 47649.77 > > samples/sec > > > > > > > > accuracy=0.999687 > > > > > > > > INFO:root:Epoch[19] Batch [500-600] Speed: 51708.12 > > samples/sec > > > > > > > > accuracy=0.999687 > > > > > > > > INFO:root:Epoch[19] Batch [600-700] Speed: 57228.63 > > samples/sec > > > > > > > > accuracy=0.999375 > > > > > > > > INFO:root:Epoch[19] Batch [700-800] Speed: 50887.85 > > samples/sec > > > > > > > > accuracy=0.999844 > > > > > > > > INFO:root:Epoch[19] Batch [800-900] Speed: 53947.98 > > samples/sec > > > > > > > > accuracy=0.999531 > > > > > > > > INFO:root:Epoch[19] Train-accuracy=0.999717 > > > > > > > > INFO:root:Epoch[19] Time cost=1.219 > > > > > > > > INFO:root:Epoch[19] Validation-accuracy=0.983977 > > > > > > > > 1011.98user 26.78system 0:31.54elapsed 3292%CPU > > (0avgtext+0avgdata > > > > > > > > 1146052maxresident)k > > > > > > > > 0inputs+0outputs (0major+3496364minor)pagefaults 0swaps > > > > > > > > > > > > > > > > Master, MKL ON: > > > > > > > > > > > > > > > > (py3_venv) piotr@ec2 cpu:1: ~/m/e/image-classification > > [master]> > > > > ldd > > > > > > > > ../../build/libmxnet.so | grep -i omp > > > > > > > > libomp.so => > > > > > > > > > > > > /home/piotr/mxnet_master/build/3rdparty/openmp/runtime/src/libomp.so > > > > > > > > (0x00007f05ba38f000) > > > > > > > > libiomp5.so => > > > > > > > > > > > > > > > > > > > > > > > > > > > > > /home/piotr/mxnet_master/build/mklml/mklml_lnx_2019.0.5.20190502/lib/libiomp5.so > > > > > > > > (0x00007f05b09f4000) > > > > > > > > > > > > > > > > INFO:root:Epoch[18] Validation-accuracy=0.982484 > > > > > > > > INFO:root:Epoch[19] Batch [0-100] Speed: 36651.63 > > samples/sec > > > > > > > > accuracy=0.999691 > > > > > > > > INFO:root:Epoch[19] Batch [100-200] Speed: 45093.98 > > samples/sec > > > > > > > > accuracy=0.999844 > > > > > > > > INFO:root:Epoch[19] Batch [200-300] Speed: 45146.84 > > samples/sec > > > > > > > > accuracy=0.999687 > > > > > > > > INFO:root:Epoch[19] Batch [300-400] Speed: 45119.90 > > samples/sec > > > > > > > > accuracy=0.999687 > > > > > > > > INFO:root:Epoch[19] Batch [400-500] Speed: 44998.96 > > samples/sec > > > > > > > > accuracy=0.999531 > > > > > > > > INFO:root:Epoch[19] Batch [500-600] Speed: 45072.25 > > samples/sec > > > > > > > > accuracy=0.999844 > > > > > > > > INFO:root:Epoch[19] Batch [600-700] Speed: 44969.79 > > samples/sec > > > > > > > > accuracy=0.999844 > > > > > > > > INFO:root:Epoch[19] Batch [700-800] Speed: 44962.78 > > samples/sec > > > > > > > > accuracy=0.999844 > > > > > > > > INFO:root:Epoch[19] Batch [800-900] Speed: 44945.47 > > samples/sec > > > > > > > > accuracy=0.999375 > > > > > > > > INFO:root:Epoch[19] Train-accuracy=0.999717 > > > > > > > > INFO:root:Epoch[19] Time cost=1.367 > > > > > > > > INFO:root:Epoch[19] Validation-accuracy=0.982783 > > > > > > > > 854.97user 847.21system 0:41.44elapsed 4106%CPU > > (0avgtext+0avgdata > > > > > > > > 1154348maxresident)k > > > > > > > > 0inputs+0outputs (0major+3624361minor)pagefaults 0swaps > > > > > > > > > > > > > > > > > > > > > > > > MKL OFF: > > > > > > > > (py3_venv) piotr@ec2 cpu:0: ~/mxnet_master [master]> grep -i > > MKL > > > > > > > > cmake_options.yml > > > > > > > > USE_MKL_IF_AVAILABLE: "OFF" # Use MKL if found > > > > > > > > USE_MKLML_MKL: "OFF" # Use MKLDNN variant of MKL (if MKL > > found) IF > > > > > > > > USE_MKL_IF_AVAILABLE AND (NOT APPLE) > > > > > > > > USE_MKLDNN: "OFF" # Use MKLDNN variant of MKL (if MKL found) > IF > > > > > > > > USE_MKL_IF_AVAILABLE AND (NOT APPLE) > > > > > > > > (py3_venv) piotr@ec2 cpu:0: ~/mxnet_master [master]> ldd > > > > > > > > build/libmxnet.so |grep -i omp > > > > > > > > libomp.so => > > > > > > > > > > > > /home/piotr/mxnet_master/build/3rdparty/openmp/runtime/src/libomp.so > > > > > > > > (0x00007fb720c54000) > > > > > > > > > > > > > > > > INFO:root:Epoch[18] Validation-accuracy=0.983479 > > > > > > > > INFO:root:Epoch[19] Batch [0-100] Speed: 46784.02 > > samples/sec > > > > > > > > accuracy=1.000000 > > > > > > > > INFO:root:Epoch[19] Batch [100-200] Speed: 48824.29 > > samples/sec > > > > > > > > accuracy=0.999687 > > > > > > > > INFO:root:Epoch[19] Batch [200-300] Speed: 49190.31 > > samples/sec > > > > > > > > accuracy=0.999687 > > > > > > > > INFO:root:Epoch[19] Batch [300-400] Speed: 51518.77 > > samples/sec > > > > > > > > accuracy=0.999844 > > > > > > > > INFO:root:Epoch[19] Batch [400-500] Speed: 51551.62 > > samples/sec > > > > > > > > accuracy=0.999844 > > > > > > > > INFO:root:Epoch[19] Batch [500-600] Speed: 49026.35 > > samples/sec > > > > > > > > accuracy=0.999844 > > > > > > > > INFO:root:Epoch[19] Batch [600-700] Speed: 49002.46 > > samples/sec > > > > > > > > accuracy=0.999375 > > > > > > > > INFO:root:Epoch[19] Batch [700-800] Speed: 48980.55 > > samples/sec > > > > > > > > accuracy=0.999687 > > > > > > > > INFO:root:Epoch[19] Batch [800-900] Speed: 47402.56 > > samples/sec > > > > > > > > accuracy=0.999844 > > > > > > > > INFO:root:Epoch[19] Train-accuracy=0.999767 > > > > > > > > INFO:root:Epoch[19] Time cost=1.259 > > > > > > > > INFO:root:Epoch[19] Validation-accuracy=0.983181 > > > > > > > > 755.36user 754.94system 0:35.89elapsed 4207%CPU > > (0avgtext+0avgdata > > > > > > > > 1147008maxresident)k > > > > > > > > 0inputs+3112outputs (0major+3568826minor)pagefaults 0swaps > > > > > > > > > > > > > > > > Let me know what you think. > > > > > > > > > > > > > > > > Link to the original PR: > > > > > > > > https://github.com/apache/incubator-mxnet/pull/12160 > > > > > > > > > > > > > > > > Thanks. > > > > > > > > > > > > > > > > On Wed, Jun 19, 2019 at 5:35 PM kellen sunderland > > > > > > > > <[email protected]> wrote: > > > > > > > > > > > > > > > > > > "if you’re linking in two then you’re doing something > wrong." > > > > > > Correct, > > > > > > > > > that's one thing I believe we've got consensus on. So > let's > > call > > > > > > that > > > > > > > > out > > > > > > > > > as a bug to be fixed. > > > > > > > > > > > > > > > > > > Let's move forward with some reproducible numbers and then > > > > discuss > > > > > > the > > > > > > > > pros > > > > > > > > > / cons of which particular OMP implementation we should > use. > > > > > > > > > > > > > > > > > > On Wed, Jun 19, 2019 at 3:06 PM Pedro Larroy < > > > > > > > > [email protected]> > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > Hi Chris > > > > > > > > > > > > > > > > > > > > I would ask you to have a bit of patience and help us > with > > your > > > > > > > > > > experience in this matter. Nobody is ignoring anything, I > > > > think we > > > > > > are > > > > > > > > > > individually gathering feedbacks and trying to understand > > the > > > > > > multiple > > > > > > > > > > contributions done to this topic including yours, then go > > step > > > > by > > > > > > > > > > step, understand what is going on and run experiments and > > > > report > > > > > > back > > > > > > > > > > to the list or the corresponding github item. It was > > suggested > > > > by > > > > > > > > > > Kellen to prepare some containers, this takes effort. > > > > > > > > > > > > > > > > > > > > Regarding your final comment, most of us also have many > > other > > > > > > things > > > > > > > > > > to do and responsibilities even if our daytime jobs might > > > > involve > > > > > > > > > > MXNet in some form or another. I think that's part of the > > > > privilege > > > > > > > > > > and responsibility of working close with an open source > > > > project and > > > > > > > > > > the magic of collaboration across organizations. Let's > all > > be > > > > > > patient > > > > > > > > > > and take some time to understand and reason about this > > topic > > > > which > > > > > > is > > > > > > > > > > not simple. Since we decided to step back and gather more > > data > > > > > > let's > > > > > > > > > > take time and do it properly. > > > > > > > > > > > > > > > > > > > > Personally I hope to find time to look again into this > > issue > > > > before > > > > > > > > > > the end of the week. > > > > > > > > > > > > > > > > > > > > Thanks. > > > > > > > > > > > > > > > > > > > > Pedro. > > > > > > > > > > > > > > > > > > > > On Wed, Jun 19, 2019 at 2:43 PM Chris Olivier < > > > > > > [email protected]> > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > if you’re linking in two then you’re doing something > > wrong. > > > > You > > > > > > can > > > > > > > > see > > > > > > > > > > by > > > > > > > > > > > my email yesterday that only one is linked in. This is > > also > > > > the > > > > > > case > > > > > > > > with > > > > > > > > > > > the mkl version built by the Makefile — only the Intel > > OMP > > > > > > library is > > > > > > > > > > used > > > > > > > > > > > (no libgomp). > > > > > > > > > > > > > > > > > > > > > > That being said, Do you have clear evidence that using > > Intel > > > > OMP > > > > > > is > > > > > > > > both > > > > > > > > > > > problematic and the situation isn’t fixable? The > burden > > of > > > > > > proof is > > > > > > > > on > > > > > > > > > > the > > > > > > > > > > > ones requesting the change — it is not my > responsibility > > to > > > > > > justify > > > > > > > > the > > > > > > > > > > > current state. There must be something “terrible” and > > > > unfixable > > > > > > to > > > > > > > > > > justify > > > > > > > > > > > a change. I have seen no proof of this in all this > time. > > > > > > > > > > > > > > > > > > > > > > On a side note, I mentioned a couple of things in my > > email > > > > > > yesterday > > > > > > > > that > > > > > > > > > > > still are not being responded to (they were also > ignored > > in > > > > the > > > > > > last > > > > > > > > > > > incarnation of this “discussion” — I have much > > experience in > > > > this > > > > > > > > matter > > > > > > > > > > to > > > > > > > > > > > assume “discussion” is a waste of my time, seeing and I > > am > > > > not > > > > > > paid > > > > > > > > to > > > > > > > > > > > “work on” mxnet like y’all are). > > > > > > > > > > > > > > > > > > > > > > -C > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Wed, Jun 19, 2019 at 10:28 AM kellen sunderland < > > > > > > > > > > > [email protected]> wrote: > > > > > > > > > > > > > > > > > > > > > > > I've also quite often seen two versions of OpenMP > > linked. > > > > I > > > > > > think > > > > > > > > we > > > > > > > > > > can > > > > > > > > > > > > all agree we probably want to avoid linking in two > > > > libraries > > > > > > that > > > > > > > > do > > > > > > > > > > > > effectively the same thing. > > > > > > > > > > > > > > > > > > > > > > > > The performance questions should be fairly straight > > > > forward to > > > > > > > > > > demonstrate > > > > > > > > > > > > right? Could we just collaborate on a few minimal > > > > Dockerfiles > > > > > > that > > > > > > > > > > show > > > > > > > > > > > > (or don't show) Intel OpenMP performance speedups > with > > the > > > > > > > > workloads > > > > > > > > > > Chris > > > > > > > > > > > > is referencing? > > > > > > > > > > > > > > > > > > > > > > > > On Wed, Jun 19, 2019 at 4:44 AM Tsukrov, Stanislav < > > > > > > > > > > > > [email protected]> wrote: > > > > > > > > > > > > > > > > > > > > > > > > > Hi, Chris! > > > > > > > > > > > > > > > > > > > > > > > > > > Stas here - I've gathered that performance data. > > > > > > > > > > > > > Sure thing, I can be wrong, but please elaborate a > > bit on > > > > > > what > > > > > > > > we are > > > > > > > > > > > > > missing. > > > > > > > > > > > > > Be assured, intentional misdirection was never a > > case. > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks a lot for being constructive. > > > > > > > > > > > > > > > > > > > > > > > > > > > Turning Intel OMP on and off (and MKL as well, > > since it > > > > > > tends > > > > > > > > to > > > > > > > > > > pull > > > > > > > > > > > > in > > > > > > > > > > > > > omp, depending which one is linked in). > > > > > > > > > > > > > > > > > > > > > > > > > > We never ever considered turning MKL off. We are on > > the > > > > same > > > > > > page > > > > > > > > > > here - > > > > > > > > > > > > > MKL is crucial for the performance. > > > > > > > > > > > > > Why should we? There's a GOMP-linked version of > MKL, > > > > that we > > > > > > can > > > > > > > > use. > > > > > > > > > > > > > > > > > > > > > > > > > > What we did - we measured, if using compilers > default > > > > OpenMP > > > > > > > > > > > > > implementation instead of referenced source code > > > > > > distribution of > > > > > > > > > > OpenMP > > > > > > > > > > > > > makes anything slower. > > > > > > > > > > > > > We have found the impact to be hardly measurable. > > > > > > > > > > > > > The difference between GOMP and iOMP is <5% on our > > > > > > benchmarks, > > > > > > > > most > > > > > > > > > > of > > > > > > > > > > > > the > > > > > > > > > > > > > time less than that. > > > > > > > > > > > > > > > > > > > > > > > > > > We just suggest to simplify the build of mxnet, by > > > > removing > > > > > > the > > > > > > > > > > > > > unnecessary dependency. > > > > > > > > > > > > > > > > > > > > > > > > > > During that we discovered for example the following > > > > amazing > > > > > > > > issue: > > > > > > > > > > > > > > > https://github.com/apache/incubator-mxnet/issues/14087 > > > > > > > > > > > > > > > > > > > > > > > > > > Best Regards > > > > > > > > > > > > > > > > > > > > > > > > > > Stas > > > > > > > > > > > > > > > > > > > > > > > > > > On 18.06.19, 18:24, "Chris Olivier" < > > > > [email protected]> > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > I am very reluctant to feed the trolls again, > and > > > > this > > > > > > will > > > > > > > > be > > > > > > > > > > teh > > > > > > > > > > > > last > > > > > > > > > > > > > time I address Pedro or Anton on the subject, > but > > > > since I > > > > > > > > think > > > > > > > > > > the > > > > > > > > > > > > > numbers > > > > > > > > > > > > > being presented are incorrect (either by te > > builders > > > > not > > > > > > > > really > > > > > > > > > > > > > understanding what they are building, or > possibly > > > > > > intentional > > > > > > > > > > > > > misdirection): > > > > > > > > > > > > > > > > > > > > > > > > > > Turning Intel OMP on and off (and MKL as well, > > since > > > > it > > > > > > > > tends to > > > > > > > > > > pull > > > > > > > > > > > > > in > > > > > > > > > > > > > omp, depending which one is linked in). > > > > > > > > > > > > > There is a HUGE difference. This is consistent > > with > > > > my > > > > > > > > > > experience > > > > > > > > > > > > > before > > > > > > > > > > > > > when it was added. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > default mnist: > > > > > > > > > > > > > > > > > > > > > > > > > > python > > ../example/image-classification/train_mnist.py > > > > > > > > > > > > > INFO:root:start with arguments > > > > Namespace(add_stn=False, > > > > > > > > > > > > batch_size=64, > > > > > > > > > > > > > disp_batches=100, dtype='float32', > > gc_threshold=0.5, > > > > > > > > > > gc_type='none', > > > > > > > > > > > > > gpus=None, image_shape='1, 28, 28', > > > > > > initializer='default', > > > > > > > > > > > > > kv_store='device', load_epoch=None, loss='', > > lr=0.05, > > > > > > > > > > lr_factor=0.1, > > > > > > > > > > > > > lr_step_epochs='10', macrobatch_size=0, > > > > > > model_prefix=None, > > > > > > > > > > mom=0.9, > > > > > > > > > > > > > monitor=0, network='mlp', num_classes=10, > > > > num_epochs=20, > > > > > > > > > > > > > num_examples=60000, num_layers=None, > > optimizer='sgd', > > > > > > > > > > > > > profile_server_suffix='', > > profile_worker_suffix='', > > > > > > > > > > save_period=1, > > > > > > > > > > > > > test_io=0, top_k=0, warmup_epochs=5, > > > > > > > > warmup_strategy='linear', > > > > > > > > > > > > > wd=0.0001) > > > > > > > > > > > > > > > > > > > > > > > > > > INTEL OMP: > > > > > > > > > > > > > > > > > > > > > > > > > > ldd libmxnet.so | grep omp > > > > > > > > > > > > > libomp.so => > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > /home/chris/src/mxnet/cmake_omp/3rdparty/openmp/runtime/src/libomp.so > > > > > > > > > > > > > (0x00007f978fde7000) > > > > > > > > > > > > > > > > > > > > > > > > > > :root:Epoch[0] Batch [0-100] Speed: > > 31548.09 > > > > > > > > samples/sec > > > > > > > > > > > > > accuracy=0.780012 > > > > > > > > > > > > > INFO:root:Epoch[0] Batch [100-200] Speed: > > > > 16073.21 > > > > > > > > > > samples/sec > > > > > > > > > > > > > accuracy=0.920469 > > > > > > > > > > > > > INFO:root:Epoch[0] Batch [200-300] Speed: > > > > 19075.91 > > > > > > > > > > samples/sec > > > > > > > > > > > > > accuracy=0.928281 > > > > > > > > > > > > > INFO:root:Epoch[0] Batch [300-400] Speed: > > > > 23211.36 > > > > > > > > > > samples/sec > > > > > > > > > > > > > accuracy=0.942813 > > > > > > > > > > > > > INFO:root:Epoch[0] Batch [400-500] Speed: > > > > 22139.79 > > > > > > > > > > samples/sec > > > > > > > > > > > > > accuracy=0.938750 > > > > > > > > > > > > > INFO:root:Epoch[0] Batch [500-600] Speed: > > > > 23225.52 > > > > > > > > > > samples/sec > > > > > > > > > > > > > accuracy=0.946562 > > > > > > > > > > > > > INFO:root:Epoch[0] Batch [600-700] Speed: > > > > 19547.41 > > > > > > > > > > samples/sec > > > > > > > > > > > > > accuracy=0.953281 > > > > > > > > > > > > > INFO:root:Epoch[0] Batch [700-800] Speed: > > > > 24111.73 > > > > > > > > > > samples/sec > > > > > > > > > > > > > accuracy=0.951562 > > > > > > > > > > > > > INFO:root:Epoch[0] Batch [800-900] Speed: > > > > 13959.88 > > > > > > > > > > samples/sec > > > > > > > > > > > > > accuracy=0.957500 > > > > > > > > > > > > > INFO:root:Epoch[0] Train-accuracy=0.925423 > > > > > > > > > > > > > INFO:root:Epoch[0] Time cost=3.806 > > > > > > > > > > > > > INFO:root:Epoch[0] Validation-accuracy=0.962580 > > > > > > > > > > > > > INFO:root:Epoch[1] Batch [0-100] Speed: > > > > 24560.21 > > > > > > > > > > samples/sec > > > > > > > > > > > > > accuracy=0.968131 > > > > > > > > > > > > > INFO:root:Epoch[1] Batch [100-200] Speed: > > > > 23457.03 > > > > > > > > > > samples/sec > > > > > > > > > > > > > accuracy=0.966250 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > LIBGOMP: > > > > > > > > > > > > > > > > > > > > > > > > > > ldd libmxnet.so | grep omp > > > > > > > > > > > > > libgomp.so.1 => > > > > > > > > /usr/lib/x86_64-linux-gnu/libgomp.so.1 > > > > > > > > > > > > > (0x00007f25c25dd000) > > > > > > > > > > > > > > > > > > > > > > > > > > INFO:root:Epoch[0] Batch [0-100] Speed: > > > > 1731.01 > > > > > > > > > > samples/sec > > > > > > > > > > > > > accuracy=0.782488 > > > > > > > > > > > > > INFO:root:Epoch[0] Batch [100-200] Speed: > > > > 3551.32 > > > > > > > > > > samples/sec > > > > > > > > > > > > > accuracy=0.907813 > > > > > > > > > > > > > INFO:root:Epoch[0] Batch [200-300] Speed: > > > > 1991.00 > > > > > > > > > > samples/sec > > > > > > > > > > > > > accuracy=0.927188 > > > > > > > > > > > > > INFO:root:Epoch[0] Batch [300-400] Speed: > > > > 2175.45 > > > > > > > > > > samples/sec > > > > > > > > > > > > > accuracy=0.937969 > > > > > > > > > > > > > INFO:root:Epoch[0] Batch [400-500] Speed: > > > > 1644.95 > > > > > > > > > > samples/sec > > > > > > > > > > > > > accuracy=0.942187 > > > > > > > > > > > > > INFO:root:Epoch[0] Batch [500-600] Speed: > > > > 6444.58 > > > > > > > > > > samples/sec > > > > > > > > > > > > > accuracy=0.950156 > > > > > > > > > > > > > INFO:root:Epoch[0] Batch [600-700] Speed: > > > > 7842.16 > > > > > > > > > > samples/sec > > > > > > > > > > > > > accuracy=0.947969 > > > > > > > > > > > > > INFO:root:Epoch[0] Batch [700-800] Speed: > > > > 9412.07 > > > > > > > > > > samples/sec > > > > > > > > > > > > > accuracy=0.953750 > > > > > > > > > > > > > INFO:root:Epoch[0] Batch [800-900] Speed: > > > > 12707.58 > > > > > > > > > > samples/sec > > > > > > > > > > > > > accuracy=0.953125 > > > > > > > > > > > > > > > > > > > > > > > > > > That being said, there's other issued beyond > > speed. > > > > The > > > > > > > > DEFAULT > > > > > > > > > > > > build > > > > > > > > > > > > > from > > > > > > > > > > > > > makefile (not CMake) uses Intel OMP mkl (I > showed > > > > > > before) and > > > > > > > > > > > > > mysteriously > > > > > > > > > > > > > it has no issues? This seems highly > suspicious. > > > > All I > > > > > > see > > > > > > > > is a > > > > > > > > > > lot > > > > > > > > > > > > of > > > > > > > > > > > > > hand-waving and conjecture and pointing to > > > > StackOverflow > > > > > > > > posts > > > > > > > > > > made > > > > > > > > > > > > by > > > > > > > > > > > > > people who may be of questionable pedigree to > > begin > > > > with. > > > > > > > > This > > > > > > > > > > > > smells > > > > > > > > > > > > > of a > > > > > > > > > > > > > Pedro-ego-fight rather than one of purely > > technical > > > > > > merit. > > > > > > > > > > Also, if > > > > > > > > > > > > > one > > > > > > > > > > > > > knows how OMP works, they would be very > > suspicious > > > > of > > > > > > the > > > > > > > > > > > > > "intermittent > > > > > > > > > > > > > hangs" claim -- that's probably just broken > race > > > > > > conditions > > > > > > > > > > elsewhere > > > > > > > > > > > > > until > > > > > > > > > > > > > proven differently. It'd tend freeze on the > > first > > > > use if > > > > > > > > > > something > > > > > > > > > > > > is > > > > > > > > > > > > > wrong (try using libgomp after a fork and see), > > since > > > > > > worker > > > > > > > > > > threads" > > > > > > > > > > > > > wouldn't be assigned/joined properly. IntelOMP > > is > > > > > > faster, > > > > > > > > but > > > > > > > > > > also > > > > > > > > > > > > has > > > > > > > > > > > > > other advantages, such as allowing OMP after a > > fork. > > > > > > > > > > > > > > > > > > > > > > > > > > I actually addressed a lot of issues and ask > for > > > > > > > > clarification > > > > > > > > > > in the > > > > > > > > > > > > > original PR's way back when, but they're all > just > > > > > > ignored. > > > > > > > > > > > > > > > > > > > > > > > > > > -Chris > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
