Stop disseminating false information: https://github.com/apache/incubator-mxnet/issues/14979
On Sat, Dec 7, 2019 at 7:04 AM Chris Olivier <[email protected]> wrote: > -1 > > mkldnn removed omp5 for licencing issues > no bugs have actually been traced to the use of llvm openmp. only an assert > caused by an actual bug in mxnet code. there are suitable workarounds. > > over time llvm omp has simply been used as a “catch all” for random > problems that aren’t related at all (such as getenv race condition in an > atfork call that isn’t even part of an omp parallel region). > > proposal is now and has always been roughly equivalent to the idea of > “comment out an assert rather than fix the bug it’s reporting”. > > Up until very recently, Makefile version of mxnet used libomp5 for YEARS > and not libgomp, with no issue reported (omp not built in debug mode), so > the equivalent configuration from CMake mysteriously causing myriads if > problems has questionable merit and smells more like a hubris situation. > > I use tensorflow as well and it links to libomp5 rather than libgomp. > > if the assert problem is really a problem, the bug being reported would be > prioritized and fixed. it should be fixed regardless. all the time spent by > some CI people trying to remove this could have simply fixed the actual bug > in a small fraction of the time. > > > On Fri, Dec 6, 2019 at 8:44 PM Lausen, Leonard <[email protected]> > wrote: > > > I think it's reasonable to assume that the Intel MKLDNN team is an > > "authorative" > > source about the issue of compilation with OpenMP and the OpenMP runtime > > library > > related issues. Thus I suggest we follow the recommendation of Intel > > MKLDNN team > > within the MXNet project. > > > > Looking through the Intel MKLDNN documentation, I find [1]: > > > > > DNNL uses OpenMP runtime library provided by the compiler. > > > > as well as > > > > > it's important to ensure that only one OpenMP runtime is used > throughout > > the > > > application. Having more than one OpenMP runtime linked to an > executable > > may > > > lead to undefined behavior including incorrect results or crashes. > > > > To keep our project maintainable and error free, I thus suggest we follow > > DNNL > > and use the OpenMP runtime library provided by the compiler. > > We have limited ressources and finding the root cause for any bugs > > resulting > > from linking multiple OpenMP libraries as currently done is, in my > > opinion. not > > a good use of time. We know it's due to undefined behavior and we know > > it's best > > practice to use OpenMP runtime library provided by the compiler. So let's > > just > > do that. > > > > I think given that MKL-DNN has also adopted the "OpenMP runtime library > > provided > > by the compiler" approach, this issue is not contentious anymore and > > qualifies > > for lazy consensus. > > > > Thus if there is no objection within 72 hours (lazy consensus), let's > drop > > bundled LLVM OpenMP from master [2]. If we find any issues due to > > droppeing the > > bundled LLVM OpenMP, we can always add it back prior to the next release. > > > > Best regards > > Leonard > > > > [1]: > > > > > https://github.com/intel/mkl-dnn/blob/433e086bf5d9e5ccfc9ec0b70322f931b6b1921d/doc/build/build_options.md#openmp > > (This is the updated reference from Anton's previous comment, based on > the > > changes in MKLDNN done in the meantime > > > https://github.com/apache/incubator-mxnet/pull/12160#issuecomment-415078066 > > ) > > [2]: Alike https://github.com/apache/incubator-mxnet/pull/12160 > > > > > > On Fri, 2019-12-06 at 12:16 -0800, Pedro Larroy wrote: > > > I will try to stay on the sidelines for now since previous > conversations > > > about OMP have not been productive here and I have spent way too much > > time > > > on this already, I'm not the first one giving up on trying to help with > > > this topic. > > > > > > I would be glad if you guys can work together and find a solution. I > will > > > just put my understanding of the big picture hoping that it helps move > it > > > forward. > > > > > > > > > Recently the intel omp library which seemed to have the best > performance > > of > > > the 3 was removed from MKL. > > > > > > - There's 3 libraries in play, GNU Omp which is shipped with gcc > (gomp), > > > LLVM openmp in 3rdparty (llvm-omp), Intel OMP when using MKL, which is > > > recently removed (iomp) > > > > > > - IOMP seems to have the best performance, there's stability issues > > > producing crashes sometimes but the impact seems relatively small for > > users > > > and developers. In general seems linking with a different OMP version > > that > > > the one shipped with the compiler is known to cause stability issues > but > > > it's done anyway. > > > > > > - LLVM-OMP used when building with CMake, not used in the PIP releases > or > > > when building with Make. Has stability issues, hangs when running in > > debug > > > mode during test execution and produces tons of assertions in debug > mode. > > > Might have some small performance gains but there is no clear cut data > > that > > > showcases significant performance gains. > > > > > > - GOMP is the version shipped with GCC and the PIP wheels without MKL, > > has > > > no stability problems. > > > > > > As a ballpark, IOMP might give 10% performance improvement in some > cases. > > > > > > We need to document well how users should tune and configure MXNet when > > > using OMP. > > > > > > As a developer, the safest bet is to use GOMP to be able to debug and > > > develop without issues. As a user of CPU inference / training you want > to > > > run MKL so depends on how the Intel guys want to do things. My > preference > > > as an engineer is always stability > speed. > > > > > > Related tickets: > > > > > > https://github.com/apache/incubator-mxnet/issues/16891 > > > > > > > > > https://github.com/apache/incubator-mxnet/issues/10856#issuecomment-562637931 > > > > > > > > > https://github.com/apache/incubator-mxnet/issues/11417 > > > > > > https://github.com/apache/incubator-mxnet/issues/15690 > > > > > > > > > > > > On Fri, Dec 6, 2019 at 12:39 AM Lausen, Leonard > > <[email protected]> > > > wrote: > > > > > > > Is this related to > > https://github.com/apache/incubator-mxnet/issues/10856? > > > > > > > > I unlocked that Github issue based on the Apache Code of Conduct > > > > > https://www.apache.org/foundation/policies/conduct#specific-guidelines > > > > > > > > > > > > On Sat, 2019-11-30 at 02:47 -0800, Pedro Larroy wrote: > > > > > (py3_venv) piotr@34-215-197-42:1:~/mxnet_1.6 (upstream_master)+$ > ldd > > > > > build/libmxnet.so| grep -i openmp > > > > > libomp.so => > > > > > /home/piotr/mxnet_1.6/build/3rdparty/openmp/runtime/src/libomp.so > > > > > (0x00007fde0991d000) > > > > > (py3_venv) piotr@34-215-197-42:0:~/mxnet_1.6 (upstream_master)+$ > > python > > > > > ~/deeplearning-benchmark/image_classification/infer_imagenet.py > > --use-rec > > > > > --batch-size 256 --dtype float32 --num-data-workers 40 --mode > hybrid > > > > > --model resnet50_v2 --use-pretrained --kvstore local > --log-interval 1 > > > > > --rec-val ~/data/val-passthrough.rec --rec-val-idx > > > > > ~/data/val-passthrough.idx > > > > > INFO:root:Namespace(batch_norm=False, batch_size=256, > > > > > data_dir='~/.mxnet/datasets/imagenet', dataset_size=32, > > dtype='float32', > > > > > kvstore='local', last_gamma=False, log_interval=1, > > logging_dir='logs', > > > > > lr=0.1, lr_decay=0.1, lr_decay_epoch='40,60', lr_mode='step', > > > > > lr_poly_power=2, mode='hybrid', model='resnet50_v2', momentum=0.9, > > > > > num_epochs=3, num_gpus=0, num_workers=40, > > > > > rec_val='/home/piotr/data/val-passthrough.rec', > > > > > rec_val_idx='/home/piotr/data/val-passthrough.idx', > > save_dir='params', > > > > > save_frequency=0, top_k=0, use_pretrained=True, use_rec=True, > > > > use_se=False, > > > > > warmup_epochs=0, warmup_lr=0.0, wd=0.0001) > > > > > [10:42:02] ../src/io/iter_image_recordio_2.cc:178: > > ImageRecordIOParser2: > > > > > /home/piotr/data/val-passthrough.rec, use 36 threads for decoding.. > > > > > INFO:root:Batch [0] > > > > > INFO:root:Top 1 accuracy: 0 > > > > > INFO:root:warmup_throughput: 5 samples/sec warmup_time 43.150922 > > > > > INFO:root:Batch [1] > > > > > INFO:root:Top 1 accuracy: 0 > > > > > INFO:root:warmup_throughput: 6 samples/sec warmup_time 37.971927 > > > > > INFO:root:Batch [2] > > > > > INFO:root:Top 1 accuracy: 0 > > > > > INFO:root:warmup_throughput: 7 samples/sec warmup_time 35.755363 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > (py3_venv) piotr@34-215-197-42:0:~/mxnet_1.6_plat_omp > > > > (upstream_master)+$ > > > > > git st > > > > > On branch upstream_master > > > > > Your branch is up to date with 'origin/upstream_master'. > > > > > > > > > > Changes not staged for commit: > > > > > (use "git add/rm <file>..." to update what will be committed) > > > > > (use "git checkout -- <file>..." to discard changes in working > > > > directory) > > > > > deleted: 3rdparty/openmp > > > > > > > > > > no changes added to commit (use "git add" and/or "git commit -a") > > > > > (py3_venv) piotr@34-215-197-42:1:~/mxnet_1.6_plat_omp > > > > (upstream_master)+$ > > > > > ldd build/libmxnet.so | grep -i omp > > > > > libgomp.so.1 => /usr/lib/x86_64-linux-gnu/libgomp.so.1 > > > > > (0x00007f941241c000) > > > > > > > > > > (py3_venv) piotr@34-215-197-42:130:~/mxnet_1.6_plat_omp > > > > (upstream_master)+$ > > > > > python > > ~/deeplearning-benchmark/image_classification/infer_imagenet.py > > > > > --use-rec --batch-size 256 --dtype float32 --num-data-workers 40 > > --mode > > > > > hybrid --model resnet50_v2 --use-pretrained --kvstore local > > > > --log-interval > > > > > 1 --rec-val ~/data/val-passthrough.rec --rec-val-idx > > > > > ~/data/val-passthrough.idx > > > > > INFO:root:warmup_throughput: 147 samples/sec warmup_time 1.735117 > > > > > INFO:root:Batch [16] > > > > > INFO:root:Top 1 accuracy: 0 > > > > > INFO:root:warmup_throughput: 143 samples/sec warmup_time 1.785760 > > > > > INFO:root:Batch [17] > > > > > INFO:root:Top 1 accuracy: 0 > > > > > INFO:root:warmup_throughput: 148 samples/sec warmup_time 1.729033 > > >
