Simd twiddles

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• Parallelize poseidon trace gen #822
• Parallelize domain eval #821
• Simd twiddles #820 👈
• Parallel fft #819
• dev

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[codecov-commenter]

Codecov Report

Attention: Patch coverage is 90.27778% with 7 lines in your changes missing coverage. Please review.

Project coverage is 92.78%. Comparing base (2a4fec2) to head (755db7c).

Files with missing lines	Patch %	Lines
crates/prover/src/core/backend/simd/circle.rs	90.27%	7 Missing ⚠️

Additional details and impacted files

@@                      Coverage Diff                       @@
##           spapini/09-05-parallel_fft     #820      +/-   ##
==============================================================
- Coverage                       92.80%   92.78%   -0.03%     
==============================================================
  Files                              89       89              
  Lines                           12103    12165      +62     
  Branches                        12103    12165      +62     
==============================================================
+ Hits                            11232    11287      +55     
- Misses                            764      771       +7     
  Partials                          107      107              

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[alonh5]

Reviewable status: 0 of 1 files reviewed, 4 unresolved discussions (waiting on @Alon-Ti, @shaharsamocha7, and @spapinistarkware)

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crates/prover/src/core/backend/simd/circle.rs line 282 at r1 (raw file):

    #[allow(clippy::int_plus_one)]
    fn precompute_twiddles(mut coset: Coset) -> TwiddleTree<Self> {

Please add a unit test to compare with the CPU implementation.

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crates/prover/src/core/backend/simd/circle.rs line 317 at r1 (raw file):

        }

        xs.push(PackedM31::from_array(extra.try_into().unwrap()));

Does this try into work because it's initialized with capacity N_LANES?

Code quote:

xs.push(PackedM31::from_array(extra.try_into().unwrap()));

---

crates/prover/src/core/backend/simd/circle.rs line 340 at r1 (raw file):

#[allow(clippy::int_plus_one)]
fn gen_coset_xs(coset: Coset, res: &mut Vec<PackedM31>) {

Can you add documentation? Maybe a reference to the algorithm

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crates/prover/src/core/backend/simd/circle.rs line 344 at r1 (raw file):

    assert!(log_size >= LOG_N_LANES);

    let initial_points = std::array::from_fn(|i| coset.at(bit_reverse_index(i, log_size)));

Can this bit reverse be done for the whole coset at once?

Code quote:

let initial_points = std::array::from_fn(|i| coset.at(bit_reverse_index(i, log_size)));