Use concrete-ntt for NTT operations
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Apple M2 on battery: $ cargo criterion ntt --features concrete-ntt
Compiling fhe-math v0.1.0-beta.8 (/Users/tancrede/git/fhe.rs/crates/fhe-math)
Compiling fhe v0.1.0-beta.8 (/Users/tancrede/git/fhe.rs/crates/fhe)
Finished bench [optimized] target(s) in 8.12s
running 0 tests
test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 4 filtered out; finished in 0.00s
ntt/forward/1024/62 time: [4.2295 µs 4.2310 µs 4.2335 µs]
change: [+31.699% +32.158% +32.656%] (p = 0.00 < 0.05)
Performance has regressed.
ntt/forward_vt/1024/62 time: [4.2292 µs 4.2308 µs 4.2333 µs]
change: [+30.739% +31.144% +31.576%] (p = 0.00 < 0.05)
Performance has regressed.
ntt/backward/1024/62 time: [4.9529 µs 4.9564 µs 4.9596 µs]
change: [+42.015% +42.382% +42.770%] (p = 0.00 < 0.05)
Performance has regressed.
ntt/backward_vt/1024/62 time: [4.9462 µs 4.9509 µs 4.9564 µs]
change: [+41.606% +41.982% +42.352%] (p = 0.00 < 0.05)
Performance has regressed.
ntt/forward/1024/16 time: [4.2616 µs 4.2904 µs 4.3288 µs]
change: [+33.286% +34.570% +36.245%] (p = 0.00 < 0.05)
Performance has regressed.
ntt/forward_vt/1024/16 time: [4.4043 µs 4.5029 µs 4.6164 µs]
change: [+35.090% +38.045% +43.124%] (p = 0.00 < 0.05)
Performance has regressed.
ntt/backward/1024/16 time: [4.9739 µs 4.9961 µs 5.0263 µs]
change: [+43.092% +43.963% +44.946%] (p = 0.00 < 0.05)
Performance has regressed.
ntt/backward_vt/1024/16 time: [4.9532 µs 4.9581 µs 4.9631 µs]
change: [+41.480% +42.032% +42.502%] (p = 0.00 < 0.05)
Performance has regressed.
ntt/forward/4096/62 time: [19.723 µs 19.757 µs 19.802 µs]
change: [+35.091% +36.112% +37.347%] (p = 0.00 < 0.05)
Performance has regressed.
ntt/forward_vt/4096/62 time: [19.873 µs 19.990 µs 20.126 µs]
change: [+34.851% +35.493% +36.214%] (p = 0.00 < 0.05)
Performance has regressed.
ntt/backward/4096/62 time: [22.864 µs 22.901 µs 22.951 µs]
change: [+44.177% +44.813% +45.415%] (p = 0.00 < 0.05)
Performance has regressed.
ntt/backward_vt/4096/62 time: [22.846 µs 22.856 µs 22.872 µs]
change: [+44.354% +44.766% +45.210%] (p = 0.00 < 0.05)
Performance has regressed.
ntt/forward/4096/16 time: [19.775 µs 19.871 µs 19.986 µs]
change: [+35.310% +36.557% +38.172%] (p = 0.00 < 0.05)
Performance has regressed.
ntt/forward_vt/4096/16 time: [19.678 µs 19.689 µs 19.702 µs]
change: [+33.242% +33.690% +34.139%] (p = 0.00 < 0.05)
Performance has regressed.
ntt/backward/4096/16 time: [22.840 µs 22.849 µs 22.861 µs]
change: [+43.660% +44.123% +44.560%] (p = 0.00 < 0.05)
Performance has regressed.
ntt/backward_vt/4096/16 time: [22.892 µs 22.960 µs 23.032 µs]
change: [+44.630% +45.081% +45.544%] (p = 0.00 < 0.05)
Performance has regressed. |
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Actually, I want to modify the concrete-ntt a little. |
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Intel(R) Xeon(R) Platinum 8275CL CPU @ 3.00GHz cargo criterion ntt --features concrete-ntt
Compiling fhe-math v0.1.0-beta.8 (/data/dev/[fhe.rs/crates/fhe-math](http://fhe.rs/crates/fhe-math))
Compiling fhe v0.1.0-beta.8 (/data/dev/[fhe.rs/crates/fhe](http://fhe.rs/crates/fhe))
Finished bench [optimized] target(s) in 4.60s
Gnuplot not found, using plotters backend
Gnuplot not found, using plotters backend
Gnuplot not found, using plotters backend
running 0 tests
test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 4 filtered out; finished in 0.00s
Gnuplot not found, using plotters backend
ntt/forward/1024/62 time: [7.9211 µs 7.9222 µs 7.9231 µs]
change: [-52.194% -52.185% -52.178%] (p = 0.00 < 0.05)
Performance has improved.
ntt/forward_vt/1024/62 time: [7.8962 µs 7.9078 µs 7.9179 µs]
change: [-48.513% -48.461% -48.413%] (p = 0.00 < 0.05)
Performance has improved.
ntt/backward/1024/62 time: [8.9256 µs 8.9387 µs 8.9510 µs]
change: [-22.332% -22.265% -22.208%] (p = 0.00 < 0.05)
Performance has improved.
ntt/backward_vt/1024/62 time: [8.8733 µs 8.8781 µs 8.8836 µs]
change: [-18.803% -18.765% -18.725%] (p = 0.00 < 0.05)
Performance has improved.
ntt/forward/1024/16 time: [7.4251 µs 7.5024 µs 7.6175 µs]
change: [-54.565% -54.342% -53.987%] (p = 0.00 < 0.05)
Performance has improved.
ntt/forward_vt/1024/16 time: [7.5126 µs 7.5287 µs 7.5420 µs]
change: [-49.884% -49.787% -49.698%] (p = 0.00 < 0.05)
Performance has improved.
ntt/backward/1024/16 time: [8.3443 µs 8.3462 µs 8.3478 µs]
change: [-27.461% -27.448% -27.436%] (p = 0.00 < 0.05)
Performance has improved.
ntt/backward_vt/1024/16 time: [8.3488 µs 8.3499 µs 8.3512 µs]
change: [-23.645% -23.601% -23.574%] (p = 0.00 < 0.05)
Performance has improved.
ntt/forward/4096/62 time: [33.557 µs 33.562 µs 33.566 µs]
change: [-55.338% -54.399% -53.716%] (p = 0.00 < 0.05)
Performance has improved.
ntt/forward_vt/4096/62 time: [34.956 µs 35.053 µs 35.149 µs]
change: [-48.215% -48.066% -47.919%] (p = 0.00 < 0.05)
Performance has improved.
ntt/backward/4096/62 time: [40.084 µs 40.110 µs 40.129 µs]
change: [-25.304% -25.241% -25.178%] (p = 0.00 < 0.05)
Performance has improved.
ntt/backward_vt/4096/62 time: [39.784 µs 39.793 µs 39.804 µs]
change: [-22.524% -22.509% -22.493%] (p = 0.00 < 0.05)
Performance has improved.
ntt/forward/4096/16 time: [35.116 µs 35.187 µs 35.243 µs]
change: [-50.887% -50.801% -50.726%] (p = 0.00 < 0.05)
Performance has improved.
ntt/forward_vt/4096/16 time: [33.574 µs 33.584 µs 33.598 µs]
change: [-49.150% -49.135% -49.119%] (p = 0.00 < 0.05)
Performance has improved.
ntt/backward/4096/16 time: [38.478 µs 38.485 µs 38.492 µs]
change: [-31.876% -29.802% -28.464%] (p = 0.00 < 0.05)
Performance has improved.
ntt/backward_vt/4096/16 time: [38.505 µs 38.513 µs 38.521 µs]
change: [-25.007% -24.990% -24.972%] (p = 0.00 < 0.05)
Performance has improved.$ cargo +nightly criterion ntt --features concrete-ntt-nightly
ntt/forward/1024/62 time: [4.0195 µs 4.0297 µs 4.0412 µs]
change: [-49.195% -49.092% -48.961%] (p = 0.00 < 0.05)
Performance has improved.
ntt/forward_vt/1024/62 time: [3.8602 µs 3.8623 µs 3.8644 µs]
change: [-51.222% -51.168% -51.109%] (p = 0.00 < 0.05)
Performance has improved.
ntt/backward/1024/62 time: [4.6452 µs 4.6559 µs 4.6658 µs]
change: [-48.186% -48.072% -47.969%] (p = 0.00 < 0.05)
Performance has improved.
ntt/backward_vt/1024/62 time: [4.4434 µs 4.4449 µs 4.4475 µs]
change: [-49.954% -49.869% -49.726%] (p = 0.00 < 0.05)
Performance has improved.
ntt/forward/1024/16 time: [4.0979 µs 4.0988 µs 4.0997 µs]
change: [-45.527% -45.114% -44.823%] (p = 0.00 < 0.05)
Performance has improved.
ntt/forward_vt/1024/16 time: [3.8746 µs 3.8767 µs 3.8787 µs]
change: [-48.519% -48.427% -48.325%] (p = 0.00 < 0.05)
Performance has improved.
ntt/backward/1024/16 time: [4.6727 µs 4.6841 µs 4.6956 µs]
change: [-43.972% -43.862% -43.766%] (p = 0.00 < 0.05)
Performance has improved.
ntt/backward_vt/1024/16 time: [4.4763 µs 4.4767 µs 4.4772 µs]
change: [-46.397% -46.388% -46.378%] (p = 0.00 < 0.05)
Performance has improved.
ntt/forward/4096/62 time: [21.465 µs 21.498 µs 21.522 µs]
change: [-35.987% -35.904% -35.851%] (p = 0.00 < 0.05)
Performance has improved.
ntt/forward_vt/4096/62 time: [20.704 µs 20.710 µs 20.717 µs]
change: [-41.233% -41.067% -40.901%] (p = 0.00 < 0.05)
Performance has improved.
ntt/backward/4096/62 time: [23.186 µs 23.228 µs 23.253 µs]
change: [-42.044% -41.976% -41.908%] (p = 0.00 < 0.05)
Performance has improved.
ntt/backward_vt/4096/62 time: [23.653 µs 23.666 µs 23.679 µs]
change: [-40.539% -40.501% -40.463%] (p = 0.00 < 0.05)
Performance has improved.
ntt/forward/4096/16 time: [18.732 µs 18.736 µs 18.741 µs]
change: [-46.796% -46.713% -46.621%] (p = 0.00 < 0.05)
Performance has improved.
ntt/forward_vt/4096/16 time: [18.746 µs 18.755 µs 18.764 µs]
change: [-44.181% -44.154% -44.126%] (p = 0.00 < 0.05)
Performance has improved.
ntt/backward/4096/16 time: [20.750 µs 20.759 µs 20.772 µs]
change: [-46.058% -45.980% -45.892%] (p = 0.00 < 0.05)
Performance has improved.
ntt/backward_vt/4096/16 time: [21.054 µs 21.056 µs 21.058 µs]
change: [-45.338% -45.325% -45.312%] (p = 0.00 < 0.05)
Performance has improved. |
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@fionser I was going to ask you to review. I fully support what you propose, it would be great to merge the normalization in |
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@tlepoint Does the benchmark means the concrete-ntt is slower ? I see, the nightly-concrete-ntt can support AVX512 which should be faster than the non-nightly one |
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It's slower on Apple M1/M2, but it's faster on Intel with AVX2/AVX512. |
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It suprised me that the concret-ntt impl is 30% slower on Apple M1/M2. Given that the concrete-ntt is quit similiar to the pointer-base implemetation in fhe.rs when n <= 1024. |
This would need to be fully investigated; but a possible reason is that this library is using "Shoup" representation for the NTT precomputed values, and limiting moduli to 62-bits maximum, which allows to speed up the base arithmetic operations. |
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Acutally, the concrete-ntt also uses Shoup's mulmod trick and Harvey’s butterfly (when the prime modulus is less than 62-bit) which is what fhe.rs doing. |
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I find my optimization expereience is not working on Rust/Apple :( // The shoup's mul that uses 2 double-width mul (i.e., fhe.rs)
pub const fn lazy_mul_shoup(&self, a: u64, b: u64, b_shoup: u64) -> u64 {
let q = ((a as u128) * (b_shoup as u128)) >> 64;
let r = ((a as u128) * (b as u128) - q * (self.p as u128)) as u64;
r
}
ntt/forward/4096/62 time: [14.730 µs 14.774 µs 14.845 µs]
change: [-26.838% -26.447% -26.049%] (p = 0.00 < 0.05)// The shoup's mul that uses only one double-width mul which is expected to be faster (i.e,. concrete-ntt)
// However, this code show slower in M2
pub const fn lazy_mul_shoup(&self, a: u64, b: u64, b_shoup: u64) -> u64 {
let q = (((a as u128) * (b_shoup as u128)) >> 64) as u64;
let q = q.wrapping_mul(self.p);
let r = a.wrapping_mul(b).wrapping_sub(q);
r
}
ntt/forward/4096/62 time: [20.120 µs 20.150 µs 20.187 µs]
This also match the benchmark on concrete-ntt. Thus, I would say the performance downgrade from fhe.rs to concrete-ntt is due to this mulmod function. It will be nice @sarah-ek can give us a hint why a such thing happens (I am a newbee to Rust) |
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I am not sure what happens either (but I can reproduce the same slowdown when using your code). It is supposed to be compiled the same way: Is concrete-ntt faster if you work with |
Yes, the concrete-ntt is faster when doing both multiplication in u128 for Apple M2. |
fionser
approved these changes
Feb 5, 2024
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We allow the use of
concrete-nttinfhe-mathcrate via the feature flagsconcrete-nttconcrete-ntt-nightlyBenchmarks to be added to this PR.