[n2d4]

I just edited my comment while you were writing your comment to add an explanation. The point here is that some primitives in eg. cudNN are non-deterministic. Whether you classify that as a race condition or not is a different question; but it's intended behaviour.

[xyzzy_plugh]

Right but that's not an inherent GPU determinism issue. It's a software issue.

https://github.com/tensorflow/tensorflow/issues/3103#issueco... is correct that it's not necessary, it's a choice.

Your line of reasoning appears to be "GPUs are inherently non-deterministic don't be quick to judge someone's code" which as far as I can tell is dead wrong.

Admittedly there are some cases and instructions that may result in non-determinism but they are inherently necessary. The author should thinking carefully before introducing non-determinism. There are many scenarios where it is irrelevant, but ultimately the issue we are discussing here isn't the GPU's fault.

[n2d4]

What I'm saying is "there are non-deterministic primitives", not "there are no deterministic primitives".

[xyzzy_plugh]

Yes, and `gettimeofday` is a non-deterministic primitive. There is nothing special about GPUs here. If you write tests that fail sometimes because you used non-deterministic primitives like gettimeofday and someone files a bug we don't throw up our hands and say "this is not a bug but due to how CPUs work." We remove the non-deterministic bit.

There's no difference here. This isn't a GPU problem.

[cpgxiii]

Except the issue is inextricably linked to GPUs. All of the work in practical DNNs exists because of the extreme parallel performance available from GPUs, and that performance is only possible with non-deterministic threading. You can't get reasonable training and inference time on existing hardware without it.

[d0mine]

1000 threads can run in parallel. It doesn't prevent us to sum their results deterministically:

    results = ThreadPool(workers=1000).imap_unordered(calc, inputs)
    print(math.fsum(results))

Due to the magic of the fsum alg, the result is deterministic whatever order we get results in. https://docs.python.org/3/library/math.html#math.fsum

[cpgxiii]

That's not the operation being performed on GPUs that is the problem. The issue is that fundamentally GPUs allow for high performance operations using atomics, but this comes at the cost of nondeterministic results. You can get deterministic results but doing so comes with a significant performance costs.

[WithinReason]

That summation is slow and would not be used in practice.

You could use just one thread on your 10000 thread GPU too and it would be deterministic, sure. Completely beside the point.

[WanderPanda]

In my experience cuBLAS is deterministic, since matmul is the most intensive part I don‘t see other reasons for non-determinism other than sloppyness (at least when just a single GPU is involved)

[microtonal]

Yeah. In curated transformers [1] we are seeing completely deterministic output across multiple popular transformer architectures on a single GPU (there can be variance between GPUs due to different kernels). Of course, it completely depends on what ops and implementations you are using. But most transformers do not use ops that are typically non-deterministic to be fast (like scatter-add).

One non-determinism we see with a temperature of 0 is that once you have quantized weights, many predicted pieces will have the same probability, including multiple pieces with the highest probability. And then the sampler (if you are not using a greedy decoder) will sample from those pieces. So, generation is non-deterministic with a temperature of 0.

In other words, a temperature of 0 is a poor man’s greedy decoding. (It is totally possible that OpenAI’s implementation switches to a greedy decoder with a temperature of 0).

[1] https://github.com/explosion/curated-transformers

[DeathArrow]

If the hardware is deterministic, so are the results. You can't generate random numbers purely in software with deterministic hardware.

[WithinReason]

The behaviour of atomic operations is definitely not deterministic. E.g. if you have a lot of atomic adds, every time you run the code you'll get a different result without a random number generator.