[WIP] Machines communicating through shared memory #1380
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georgwiese
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This was referenced May 20, 2024
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Cherry-picked ef6a72f from #1380. With this PR, we track whether a call to a machine led to some side effect (e.g. added a block). In that case, the processed identity should count has having led to some progress, even if no values were returned to the calling machine. An example would be writing values to memory, which does not return any values and hence does not change the state of the caller.
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*Cherry-picked b1a07bd from #1380, and extended on it.* Fixes #1382. With this PR, a lookup like `selector { byte_lower + 256 * byte_upper } in { <some other machine> }` works, even if the range constraints on `byte_lower` and `byte_upper` are not "global". For example, they could be implemented as `selector { byte_lower } in { BYTES }` (i.e., `byte_lower` is only range constrained when the machine call is active). To make this work, I changed the `Machine::process_plookup` interface like this: ```diff fn process_plookup<'b, Q: QueryCallback<T>>( &mut self, mutable_state: &'b mut MutableState<'a, 'b, T, Q>, identity_id: u64, - args: &[AffineExpression<&'a AlgebraicReference, T>], + caller_rows: &'b RowPair<'b, 'a, T>, ) -> EvalResult<'a, T>; ``` The `RowPair` passed by the caller contains all range constraints known at runtime. The LHS of the lookup (or permutation) is no longer evaluated by the caller but by the callee. For this, the callee needs to remember the identity associated with the `identity_id` (before this PR, most machines just remembered the RHS, not the full identity). I don't expect there to be any performance implications, because we only invoke one machine (since #1154). ### Benchmark results ``` executor-benchmark/keccak time: [14.609 s 14.645 s 14.678 s] change: [-2.5984% -2.3127% -2.0090%] (p = 0.00 < 0.05) Performance has improved. executor-benchmark/many_chunks_chunk_0 time: [39.299 s 39.380 s 39.452 s] change: [-3.9505% -3.6909% -3.4063%] (p = 0.00 < 0.05) Performance has improved. ``` --------- Co-authored-by: Leo <leo@powdrlabs.com>
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Building on #1356, this PR re-writes some of the std machines to communicate via a shared memory.
To test:
Next steps:
While the arithmetic machine clearly benefits from this approach, it is less obvious if it is also beneficial for the Poseidon machines. They have fewer arguments to start with, and I needed to add more witness columns (one for each state element, so that the input state is available in all rows) and fixed columns (a clock). The arithmetic machine had all that already anyway.