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competitive/math/number_theoretic_transform/ntt_simd/
ntt_avx2.rs

1use super::*;
2
3#[inline]
4#[target_feature(enable = "avx2")]
5unsafe fn load_ntt_avx2(p: *const u32, step: usize) -> __m256i {
6    if step == 4 {
7        _mm256_castsi128_si256(_mm_loadu_si128(p.cast()))
8    } else {
9        _mm256_loadu_si256(p.cast())
10    }
11}
12#[inline]
13#[target_feature(enable = "avx2")]
14unsafe fn store_ntt_avx2(p: *mut u32, value: __m256i, step: usize) {
15    if step == 4 {
16        _mm_storeu_si128(p.cast(), _mm256_castsi256_si128(value));
17    } else {
18        _mm256_storeu_si256(p.cast(), value);
19    }
20}
21
22#[target_feature(enable = "avx2")]
23pub unsafe fn ntt_four_avx2<M, const INVERSE: bool>(a: &mut [u32])
24where
25    M: Montgomery32NttModulus,
26{
27    let roots = if INVERSE {
28        &M::INFO.inv_root
29    } else {
30        &M::INFO.root
31    };
32    let rates = &const {
33        let info = M::INFO;
34        let (roots, rates) = if INVERSE {
35            (info.inv_root, info.inv_rate3_packed)
36        } else {
37            (info.root, info.rate3_packed)
38        };
39        let mut result = [[0u32; 4]; 32];
40        let mut i = 0;
41        while i < 32 {
42            let r = mod_mul(rates[i][1], roots[3], M::MOD, M::R);
43            let r2 = mod_mul(r, r, M::MOD, M::R);
44            result[i] = [M::N1, r, r2, mod_mul(r2, r, M::MOD, M::R)];
45            i += 1;
46        }
47        result
48    };
49    let one = _mm256_set1_epi32(M::N1 as i32);
50    let modulus = _mm256_set1_epi32(M::MOD as i32);
51    let modulus2 = _mm256_set1_epi32((M::MOD * 2) as i32);
52    let r = _mm256_set1_epi32(M::R as i32);
53    let root3 = M::mod_mul(roots[2], roots[3]) as i32;
54    let step = _mm256_setr_epi32(
55        M::N1 as i32,
56        roots[3] as i32,
57        roots[2] as i32,
58        root3,
59        M::N1 as i32,
60        roots[3] as i32,
61        roots[2] as i32,
62        root3,
63    );
64    let mut twiddle = _mm256_blend_epi32::<0xf0>(one, step);
65    let imag = if INVERSE {
66        _mm256_setr_epi32(
67            M::N1 as i32,
68            roots[2] as i32,
69            M::N1 as i32,
70            roots[2] as i32,
71            M::N1 as i32,
72            roots[2] as i32,
73            M::N1 as i32,
74            roots[2] as i32,
75        )
76    } else {
77        _mm256_setr_epi32(
78            M::N1 as i32,
79            M::N1 as i32,
80            roots[2] as i32,
81            roots[2] as i32,
82            M::N1 as i32,
83            M::N1 as i32,
84            roots[2] as i32,
85            roots[2] as i32,
86        )
87    };
88    for (s, a) in a.as_chunks_mut::<8>().0.iter_mut().enumerate() {
89        let mut x = _mm256_loadu_si256(a.as_ptr().cast());
90        if !INVERSE {
91            x = montgomery_simd::montgomery_mul_256(x, twiddle, r, modulus);
92        }
93        let pair = if INVERSE {
94            let y = _mm256_shuffle_epi32::<0xb1>(x);
95            let sum = montgomery_simd::montgomery_add_256(x, y, modulus2);
96            let diff = montgomery_simd::montgomery_sub_256(x, y, modulus2);
97            let sum = _mm256_shuffle_epi32::<0x88>(sum);
98            let diff = _mm256_shuffle_epi32::<0x88>(diff);
99            let diff = montgomery_simd::montgomery_mul_256(diff, imag, r, modulus);
100            _mm256_unpacklo_epi64(sum, diff)
101        } else {
102            let y = _mm256_shuffle_epi32::<0x4e>(x);
103            let sum = montgomery_simd::montgomery_add_256(x, y, modulus2);
104            let diff = montgomery_simd::montgomery_sub_256(x, y, modulus2);
105            _mm256_unpacklo_epi64(sum, diff)
106        };
107        let left = _mm256_shuffle_epi32::<0xa0>(pair);
108        let mut right = _mm256_shuffle_epi32::<0xf5>(pair);
109        if !INVERSE {
110            right = montgomery_simd::montgomery_mul_256(right, imag, r, modulus);
111        }
112        let sum = montgomery_simd::montgomery_add_256(left, right, modulus2);
113        let diff = montgomery_simd::montgomery_sub_256(left, right, modulus2);
114        let mut value = _mm256_blend_epi32::<0xaa>(sum, diff);
115        if INVERSE {
116            value = _mm256_shuffle_epi32::<0xd8>(value);
117            value = montgomery_simd::montgomery_mul_256(value, twiddle, r, modulus);
118        }
119        _mm256_storeu_si256(a.as_mut_ptr().cast(), value);
120        let rate = _mm256_broadcastsi128_si256(_mm_loadu_si128(
121            rates[s.trailing_ones() as usize + 1].as_ptr().cast(),
122        ));
123        twiddle = montgomery_simd::montgomery_mul_256(twiddle, rate, r, modulus);
124    }
125}
126
127#[target_feature(enable = "avx2")]
128unsafe fn normalize_avx2<M>(a: &mut [u32])
129where
130    M: Montgomery32NttModulus,
131{
132    let mod_vec = _mm256_set1_epi32(M::MOD as i32);
133    let mut i = 0;
134    while i + 8 <= a.len() {
135        let x = _mm256_loadu_si256(a.as_ptr().add(i) as *const __m256i);
136        let y = _mm256_min_epu32(x, _mm256_sub_epi32(x, mod_vec));
137        _mm256_storeu_si256(a.as_mut_ptr().add(i) as *mut __m256i, y);
138        i += 8;
139    }
140    while i < a.len() {
141        a[i] = normalize_scalar::<M>(a[i]);
142        i += 1;
143    }
144}
145
146pub unsafe fn add_vec_avx2<M>(
147    a: __m256i,
148    b: __m256i,
149    mod_vec: __m256i,
150    mod2_vec: __m256i,
151) -> __m256i
152where
153    M: Montgomery32NttModulus,
154{
155    if M::MOD < LAZY_THRESHOLD {
156        montgomery_simd::montgomery_add_256(a, b, mod2_vec)
157    } else {
158        montgomery_simd::add_mod_256(a, b, mod_vec)
159    }
160}
161
162pub unsafe fn sub_vec_avx2<M>(
163    a: __m256i,
164    b: __m256i,
165    mod_vec: __m256i,
166    mod2_vec: __m256i,
167) -> __m256i
168where
169    M: Montgomery32NttModulus,
170{
171    if M::MOD < LAZY_THRESHOLD {
172        montgomery_simd::montgomery_sub_256(a, b, mod2_vec)
173    } else {
174        montgomery_simd::sub_mod_256(a, b, mod_vec)
175    }
176}
177
178unsafe fn mul_vec_avx2<M>(a: __m256i, b: __m256i, r_vec: __m256i, mod_vec: __m256i) -> __m256i
179where
180    M: Montgomery32NttModulus,
181{
182    if M::MOD < LAZY_THRESHOLD {
183        montgomery_simd::montgomery_mul_256(a, b, r_vec, mod_vec)
184    } else {
185        montgomery_simd::montgomery_mul_256_canon(a, b, r_vec, mod_vec)
186    }
187}
188
189#[target_feature(enable = "avx2")]
190pub unsafe fn pointwise_multiply_avx2<M>(f: &mut [MInt<M>], g: &[MInt<M>])
191where
192    M: Montgomery32NttModulus,
193{
194    let r_vec = _mm256_set1_epi32(M::R as i32);
195    let mod_vec = _mm256_set1_epi32(M::MOD as i32);
196    let mut i = 0;
197    while i + 8 <= f.len() {
198        let a = _mm256_loadu_si256(f.as_ptr().add(i) as *const __m256i);
199        let b = _mm256_loadu_si256(g.as_ptr().add(i) as *const __m256i);
200        let x = montgomery_simd::montgomery_mul_256_canon(a, b, r_vec, mod_vec);
201        _mm256_storeu_si256(f.as_mut_ptr().add(i) as *mut __m256i, x);
202        i += 8;
203    }
204    while i < f.len() {
205        f[i] *= g[i];
206        i += 1;
207    }
208}
209
210#[target_feature(enable = "avx2")]
211pub unsafe fn pointwise_multiply_add_avx2<M>(sum: &mut [MInt<M>], f: &[MInt<M>], g: &[MInt<M>])
212where
213    M: Montgomery32NttModulus,
214{
215    let r_vec = _mm256_set1_epi32(M::R as i32);
216    let mod_vec = _mm256_set1_epi32(M::MOD as i32);
217    let mut i = 0;
218    while i + 8 <= sum.len() {
219        let s = _mm256_loadu_si256(sum.as_ptr().add(i).cast());
220        let f = _mm256_loadu_si256(f.as_ptr().add(i).cast());
221        let g = _mm256_loadu_si256(g.as_ptr().add(i).cast());
222        let product = montgomery_simd::montgomery_mul_256_canon(f, g, r_vec, mod_vec);
223        _mm256_storeu_si256(
224            sum.as_mut_ptr().add(i).cast(),
225            montgomery_simd::add_mod_256(s, product, mod_vec),
226        );
227        i += 8;
228    }
229    while i < sum.len() {
230        sum[i] += f[i] * g[i];
231        i += 1;
232    }
233}
234
235#[inline]
236#[target_feature(enable = "avx2")]
237pub unsafe fn ntt_batch_avx2<M, const PARTIAL: bool>(a: &mut [MInt<M>], width: usize)
238where
239    M: Montgomery32NttModulus,
240{
241    let n = a.len() / width;
242    if n <= 1 {
243        return;
244    }
245    let ptr = a.as_mut_ptr() as *mut u32;
246    let a = std::slice::from_raw_parts_mut(ptr, a.len());
247    let mod_vec = _mm256_set1_epi32(M::MOD as i32);
248    let mod2_vec = _mm256_set1_epi32(M::MOD.wrapping_add(M::MOD) as i32);
249    let r_vec = _mm256_set1_epi32(M::R as i32);
250    let imag = M::INFO.root[2];
251    let imag_vec = _mm256_set1_epi32(imag as i32);
252
253    let mut v = n / 2;
254    if n.trailing_zeros() & 1 == 1 {
255        let half = v * width;
256        let step = if PARTIAL && half == 4 { 4 } else { 8 };
257        let mut i = 0;
258        while i + step <= half {
259            let x0 = load_ntt_avx2(a.as_ptr().add(i), step);
260            let x1 = load_ntt_avx2(a.as_ptr().add(half + i), step);
261            let y0 = add_vec_avx2::<M>(x0, x1, mod_vec, mod2_vec);
262            let y1 = sub_vec_avx2::<M>(x0, x1, mod_vec, mod2_vec);
263            store_ntt_avx2(a.as_mut_ptr().add(i), y0, step);
264            store_ntt_avx2(a.as_mut_ptr().add(half + i), y1, step);
265            i += step;
266        }
267        while i < half {
268            let x0 = a[i];
269            let x1 = a[half + i];
270            a[i] = add_scalar::<M>(x0, x1);
271            a[half + i] = sub_scalar::<M>(x0, x1);
272            i += 1;
273        }
274        v >>= 1;
275    }
276    while v > 1 {
277        if width == 1 && v == 2 && a.len() >= 8 && M::MOD < LAZY_THRESHOLD {
278            ntt_four_avx2::<M, false>(a);
279            break;
280        }
281        let half = (v >> 1) * width;
282        let step = if PARTIAL && half == 4 { 4 } else { 8 };
283        let mut w1 = M::N1;
284        let mut w2 = w1;
285        let mut w3 = w1;
286        for (s, block) in a.chunks_exact_mut((v << 1) * width).enumerate() {
287            let base = block.as_mut_ptr();
288            let ll = base;
289            let lr = base.add(half);
290            let rl = base.add(v * width);
291            let rr = base.add(v * width + half);
292
293            let w1v = _mm256_set1_epi32(w1 as i32);
294            let w2v = _mm256_set1_epi32(w2 as i32);
295            let w3v = _mm256_set1_epi32(w3 as i32);
296
297            let mut i = 0;
298            while i + step <= half {
299                let x0 = load_ntt_avx2(ll.add(i), step);
300                let x1 = load_ntt_avx2(lr.add(i), step);
301                let x2 = load_ntt_avx2(rl.add(i), step);
302                let x3 = load_ntt_avx2(rr.add(i), step);
303
304                let (a1, a2, a3) = if s == 0 {
305                    (x1, x2, x3)
306                } else {
307                    (
308                        mul_vec_avx2::<M>(x1, w1v, r_vec, mod_vec),
309                        mul_vec_avx2::<M>(x2, w2v, r_vec, mod_vec),
310                        mul_vec_avx2::<M>(x3, w3v, r_vec, mod_vec),
311                    )
312                };
313
314                let a0pa2 = add_vec_avx2::<M>(x0, a2, mod_vec, mod2_vec);
315                let a0na2 = sub_vec_avx2::<M>(x0, a2, mod_vec, mod2_vec);
316                let a1pa3 = add_vec_avx2::<M>(a1, a3, mod_vec, mod2_vec);
317                let a1na3 = sub_vec_avx2::<M>(a1, a3, mod_vec, mod2_vec);
318                let a1na3imag = mul_vec_avx2::<M>(a1na3, imag_vec, r_vec, mod_vec);
319
320                let y0 = add_vec_avx2::<M>(a0pa2, a1pa3, mod_vec, mod2_vec);
321                let y1 = sub_vec_avx2::<M>(a0pa2, a1pa3, mod_vec, mod2_vec);
322                let y2 = add_vec_avx2::<M>(a0na2, a1na3imag, mod_vec, mod2_vec);
323                let y3 = sub_vec_avx2::<M>(a0na2, a1na3imag, mod_vec, mod2_vec);
324
325                store_ntt_avx2(ll.add(i), y0, step);
326                store_ntt_avx2(lr.add(i), y1, step);
327                store_ntt_avx2(rl.add(i), y2, step);
328                store_ntt_avx2(rr.add(i), y3, step);
329                i += step;
330            }
331            while i < half {
332                let a0 = *ll.add(i);
333                let a1 = mul_scalar::<M>(*lr.add(i), w1);
334                let a2 = mul_scalar::<M>(*rl.add(i), w2);
335                let a3 = mul_scalar::<M>(*rr.add(i), w3);
336                let a0pa2 = add_scalar::<M>(a0, a2);
337                let a0na2 = sub_scalar::<M>(a0, a2);
338                let a1pa3 = add_scalar::<M>(a1, a3);
339                let a1na3 = sub_scalar::<M>(a1, a3);
340                let a1na3imag = mul_scalar::<M>(a1na3, imag);
341                *ll.add(i) = add_scalar::<M>(a0pa2, a1pa3);
342                *lr.add(i) = sub_scalar::<M>(a0pa2, a1pa3);
343                *rl.add(i) = add_scalar::<M>(a0na2, a1na3imag);
344                *rr.add(i) = sub_scalar::<M>(a0na2, a1na3imag);
345                i += 1;
346            }
347            let rate = &M::INFO.rate3_packed[s.trailing_ones() as usize];
348            w1 = M::mod_mul(w1, rate[1]);
349            w2 = M::mod_mul(w2, rate[3]);
350            w3 = M::mod_mul(w3, rate[5]);
351        }
352        v >>= 2;
353    }
354    normalize_avx2::<M>(a);
355}
356
357#[inline]
358#[target_feature(enable = "avx2")]
359pub unsafe fn intt_batch_avx2<M, const PARTIAL: bool>(a: &mut [MInt<M>], width: usize)
360where
361    M: Montgomery32NttModulus,
362{
363    let n = a.len() / width;
364    if n <= 1 {
365        return;
366    }
367    let ptr = a.as_mut_ptr() as *mut u32;
368    let a = std::slice::from_raw_parts_mut(ptr, a.len());
369    let mod_vec = _mm256_set1_epi32(M::MOD as i32);
370    let mod2_vec = _mm256_set1_epi32(M::MOD.wrapping_add(M::MOD) as i32);
371    let r_vec = _mm256_set1_epi32(M::R as i32);
372    let iimag = M::INFO.inv_root[2];
373    let iimag_vec = _mm256_set1_epi32(iimag as i32);
374
375    let mut v = 1;
376    if width == 1 && a.len() >= 8 && M::MOD < LAZY_THRESHOLD {
377        ntt_four_avx2::<M, true>(a);
378        v = 4;
379    }
380    let limit = if n.trailing_zeros() & 1 == 1 {
381        n / 2
382    } else {
383        n
384    };
385    while v < limit {
386        let quarter = v * width;
387        let step = if PARTIAL && quarter == 4 { 4 } else { 8 };
388        let mut w1 = M::N1;
389        let mut w2 = w1;
390        let mut w3 = w1;
391        for (s, block) in a.chunks_exact_mut((v << 2) * width).enumerate() {
392            let base = block.as_mut_ptr();
393            let ll = base;
394            let lr = base.add(quarter);
395            let rl = base.add(quarter * 2);
396            let rr = base.add(quarter * 3);
397
398            let w1v = _mm256_set1_epi32(w1 as i32);
399            let w2v = _mm256_set1_epi32(w2 as i32);
400            let w3v = _mm256_set1_epi32(w3 as i32);
401
402            let mut i = 0;
403            while i + step <= quarter {
404                let x0 = load_ntt_avx2(ll.add(i), step);
405                let x1 = load_ntt_avx2(lr.add(i), step);
406                let x2 = load_ntt_avx2(rl.add(i), step);
407                let x3 = load_ntt_avx2(rr.add(i), step);
408
409                let a0pa1 = add_vec_avx2::<M>(x0, x1, mod_vec, mod2_vec);
410                let a0na1 = sub_vec_avx2::<M>(x0, x1, mod_vec, mod2_vec);
411                let a2pa3 = add_vec_avx2::<M>(x2, x3, mod_vec, mod2_vec);
412                let a2na3 = sub_vec_avx2::<M>(x2, x3, mod_vec, mod2_vec);
413                let a2na3iimag = mul_vec_avx2::<M>(a2na3, iimag_vec, r_vec, mod_vec);
414
415                let y0 = add_vec_avx2::<M>(a0pa1, a2pa3, mod_vec, mod2_vec);
416                let y1 = add_vec_avx2::<M>(a0na1, a2na3iimag, mod_vec, mod2_vec);
417                let y2 = sub_vec_avx2::<M>(a0pa1, a2pa3, mod_vec, mod2_vec);
418                let y3 = sub_vec_avx2::<M>(a0na1, a2na3iimag, mod_vec, mod2_vec);
419
420                let (y1, y2, y3) = if s == 0 {
421                    (y1, y2, y3)
422                } else {
423                    (
424                        mul_vec_avx2::<M>(y1, w1v, r_vec, mod_vec),
425                        mul_vec_avx2::<M>(y2, w2v, r_vec, mod_vec),
426                        mul_vec_avx2::<M>(y3, w3v, r_vec, mod_vec),
427                    )
428                };
429
430                store_ntt_avx2(ll.add(i), y0, step);
431                store_ntt_avx2(lr.add(i), y1, step);
432                store_ntt_avx2(rl.add(i), y2, step);
433                store_ntt_avx2(rr.add(i), y3, step);
434                i += step;
435            }
436            while i < quarter {
437                let a0 = *ll.add(i);
438                let a1 = *lr.add(i);
439                let a2 = *rl.add(i);
440                let a3 = *rr.add(i);
441                let a0pa1 = add_scalar::<M>(a0, a1);
442                let a0na1 = sub_scalar::<M>(a0, a1);
443                let a2pa3 = add_scalar::<M>(a2, a3);
444                let a2na3iimag = mul_scalar::<M>(sub_scalar::<M>(a2, a3), iimag);
445                *ll.add(i) = add_scalar::<M>(a0pa1, a2pa3);
446                *lr.add(i) = mul_scalar::<M>(add_scalar::<M>(a0na1, a2na3iimag), w1);
447                *rl.add(i) = mul_scalar::<M>(sub_scalar::<M>(a0pa1, a2pa3), w2);
448                *rr.add(i) = mul_scalar::<M>(sub_scalar::<M>(a0na1, a2na3iimag), w3);
449                i += 1;
450            }
451            let rate = &M::INFO.inv_rate3_packed[s.trailing_ones() as usize];
452            w1 = M::mod_mul(w1, rate[1]);
453            w2 = M::mod_mul(w2, rate[3]);
454            w3 = M::mod_mul(w3, rate[5]);
455        }
456        v <<= 2;
457    }
458    if n.trailing_zeros() & 1 == 1 {
459        let half = (n >> 1) * width;
460        let step = if PARTIAL && half == 4 { 4 } else { 8 };
461        let mut i = 0;
462        while i + step <= half {
463            let x0 = load_ntt_avx2(a.as_ptr().add(i), step);
464            let x1 = load_ntt_avx2(a.as_ptr().add(half + i), step);
465            let y0 = add_vec_avx2::<M>(x0, x1, mod_vec, mod2_vec);
466            let y1 = sub_vec_avx2::<M>(x0, x1, mod_vec, mod2_vec);
467            store_ntt_avx2(a.as_mut_ptr().add(i), y0, step);
468            store_ntt_avx2(a.as_mut_ptr().add(half + i), y1, step);
469            i += step;
470        }
471        while i < half {
472            let x0 = a[i];
473            let x1 = a[half + i];
474            a[i] = add_scalar::<M>(x0, x1);
475            a[half + i] = sub_scalar::<M>(x0, x1);
476            i += 1;
477        }
478    }
479    let inv = M::mod_inv(<M as MIntConvert<u32>>::from(n as u32));
480    let inv_vec = _mm256_set1_epi32(inv as i32);
481    let mut i = 0;
482    while i + 8 <= a.len() {
483        let x = _mm256_loadu_si256(a.as_ptr().add(i) as *const __m256i);
484        let y = montgomery_simd::montgomery_mul_256_canon(x, inv_vec, r_vec, mod_vec);
485        _mm256_storeu_si256(a.as_mut_ptr().add(i) as *mut __m256i, y);
486        i += 8;
487    }
488    while i < a.len() {
489        a[i] = M::mod_mul(a[i], inv);
490        i += 1;
491    }
492}