deterministic runtime with pseudo-random-number generator?

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Jason E. Aten

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May 13, 2025, 9:53:07 PMMay 13
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I'd like to run variations of my Raft test code on a fully 
deterministic runtime (meaning only one thread, all 
randomness from a pseudo RNG controlled with a repeatable seed). 
I was looking at the standard (big) Go runtime, and I don't
see where there are any options to control the random number
generator there used for choosing a select, for instance,
but maybe I've missed some already available option? 
Setting GOMAXPROC=1 apparently does not prevent other background threads
for GC, OS calls, etc... do I understand that right?

Trying to figure out if it would a smaller lift to hack some support into TinyGo,
whose typically microcontroller targets are single threaded, as
that would give me a big head start, or if the big Go runtime 
places that would need pseudo RNGs replaced
are isolated enough for it do be doable (in a hacked up, non-supported
version, of course)... big Go would have better compatibility with
production code of course, but TinyGo is already more conceptually
aligned, and might be easier to maintain if the experiment is successful...

Thoughts?

Robert Engels

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May 13, 2025, 10:13:15 PMMay 13
to Jason E. Aten, golang-nuts
Pretty sure you cannot do this for two reasons: the runtime creates internal threads for IO and other purposes that you cannot control. Also the kernel IO / poll is non deterministic. 

You might have better luck with a custom tiny Go. 

On May 13, 2025, at 1:53 PM, Jason E. Aten <j.e....@gmail.com> wrote:

I'd like to run variations of my Raft test code on a fully 
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Axel Wagner

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May 13, 2025, 10:54:37 PMMay 13
to Jason E. Aten, golang-nuts
It used to be possible to do this using NaCl. In fact, the playground used to be implemented using that and was fully deterministic.
These days, the playground uses gVisor, AFAIK, and is no longer deterministic. I don't know how well the NaCl port is still maintained.
Come to think of it, you might also try wasm. It's single-threaded and I believe you can pretty much entirely control its interaction with the outside world.

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Brian Candler

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May 15, 2025, 12:24:55 AMMay 15
to golang-nuts
Have you seen this?
I don't think it addresses random seeds, but it might help with deterministic, lock-step execution for tests.

Axel Wagner

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May 15, 2025, 12:34:30 AMMay 15
to Brian Candler, golang-nuts
On Wed, 14 May 2025 at 23:25, 'Brian Candler' via golang-nuts <golan...@googlegroups.com> wrote:
Have you seen this?

That thread was posted by OP, so yes, I assume they have seen it ;)
 
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