On Thu, Mar 23, 2023 at 1:55 AM Clemens Brunner <clemens.brun...@gmail.com> wrote:
> Hello! > > I recently got a new MacBook Pro with an M2 Pro CPU (ARM64). When I ran > some numerical computations (ICA to be precise), I was surprised how slow > it was - way slower than e.g. my almost 10 year old Intel Mac. It turns out > that the default OpenBLAS, which is what you get when installing the binary > wheel with pip (i.e. "pip install numpy"), is the reason why computations > are so slow. > > When installing NumPy from source (by using "pip install --no-binary :all: > --no-use-pep517 numpy"), it uses the Apple-provided Accelerate framework, > which includes an optimized BLAS library. The difference is mind-boggling, > I'd even say that NumPy is pretty much unusable with the default OpenBLAS > backend (at least for the applications I tested). > > In my test with four different ICA algorithms, I got these runtimes with > the default OpenBLAS: > > - FastICA: 6.3s > - Picard: 26.3s > - Infomax: 0.8s > - Extended Infomax: 1.4s > > Especially the second algorithm is way slower than on my 10 year old Intel > Mac using OpenBLAS. > > Here are the times with Accelerate: > > - FastICA: 0.4s > - Picard: 0.6s > - Infomax: 1.0s > - Extended Infomax: 1.3s > > Given this huge performance difference, my question is if you would > consider distributing a binary wheel for ARM64-based Macs which links to > Accelerate. Or are there any caveats why you do not want to do that? I know > that NumPy moved away from Accelerate years ago on Intel Macs, but maybe > now is the time to reconsider this decision. > Hi Clemens, thanks for the suggestion and benchmarks. We actually discussed this in the last community meeting. Accelerate as of today is supported when building from source, and that will use 32-bit BLAS/LAPACK (the LP64 interface). Since NumPy 1.22 we're shipping our wheels with the 64-bit (ILP64) interface, which Accelerate doesn't provide. That's about to change though, in macOS 13.3: https://developer.apple.com/documentation/macos-release-notes/macos-13_3-release-notes#Accelerate. That release will also upgrade to LAPACK 3.9.1, which means we can re-enable it for SciPy too. For macOS 14 we will most likely, if things go well, ship wheels linked against the new ILP64 Accelerate build. Due to packaging limitations (the `packaging` library ignores minor versions of macOS), we can't ship wheels for >=13.3, only >=14. Cheers, Ralf
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