diff options
author | Abseil Team <absl-team@google.com> | 2018-09-27 12:24:54 -0700 |
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committer | Derek Mauro <dmauro@google.com> | 2018-09-27 15:28:12 -0400 |
commit | 48cd2c3f351ff188bc85684b84a91b6e6d17d896 (patch) | |
tree | 6f92b0cbb0f8282b7df1cd567cb66406fbbb6f80 /absl/hash/internal/city.cc | |
parent | e291c279e458761e77a69b09b129d3d1e81f1e80 (diff) |
Export of internal Abseil changes.
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4eacae3ff1b14b1d309e8092185bc10e8a6203cf by Derek Mauro <dmauro@google.com>:
Release SwissTable - a fast, efficient, cache-friendly hash table.
https://www.youtube.com/watch?v=ncHmEUmJZf4
PiperOrigin-RevId: 214816527
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df8c3dfab3cfb2f4365909a84d0683b193cfbb11 by Derek Mauro <dmauro@google.com>:
Internal change
PiperOrigin-RevId: 214785288
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1eabd5266bbcebc33eecc91e5309b751856a75c8 by Abseil Team <absl-team@google.com>:
Internal change
PiperOrigin-RevId: 214722931
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2ebbfac950f83146b46253038e7dd7dcde9f2951 by Derek Mauro <dmauro@google.com>:
Internal change
PiperOrigin-RevId: 214701684
GitOrigin-RevId: 4eacae3ff1b14b1d309e8092185bc10e8a6203cf
Change-Id: I9ba64e395b22ad7863213d157b8019b082adc19d
Diffstat (limited to 'absl/hash/internal/city.cc')
-rw-r--r-- | absl/hash/internal/city.cc | 589 |
1 files changed, 589 insertions, 0 deletions
diff --git a/absl/hash/internal/city.cc b/absl/hash/internal/city.cc new file mode 100644 index 00000000..591017ab --- /dev/null +++ b/absl/hash/internal/city.cc @@ -0,0 +1,589 @@ +// Copyright 2018 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. +// +// This file provides CityHash64() and related functions. +// +// It's probably possible to create even faster hash functions by +// writing a program that systematically explores some of the space of +// possible hash functions, by using SIMD instructions, or by +// compromising on hash quality. + +#include "absl/hash/internal/city.h" + +#include <string.h> // for memcpy and memset +#include <algorithm> + +#include "absl/base/config.h" +#include "absl/base/internal/endian.h" +#include "absl/base/internal/unaligned_access.h" +#include "absl/base/optimization.h" + +namespace absl { +namespace hash_internal { + +#ifdef ABSL_IS_BIG_ENDIAN +#define uint32_in_expected_order(x) (absl::gbswap_32(x)) +#define uint64_in_expected_order(x) (absl::gbswap_64(x)) +#else +#define uint32_in_expected_order(x) (x) +#define uint64_in_expected_order(x) (x) +#endif + +static uint64_t Fetch64(const char *p) { + return uint64_in_expected_order(ABSL_INTERNAL_UNALIGNED_LOAD64(p)); +} + +static uint32_t Fetch32(const char *p) { + return uint32_in_expected_order(ABSL_INTERNAL_UNALIGNED_LOAD32(p)); +} + +// Some primes between 2^63 and 2^64 for various uses. +static const uint64_t k0 = 0xc3a5c85c97cb3127ULL; +static const uint64_t k1 = 0xb492b66fbe98f273ULL; +static const uint64_t k2 = 0x9ae16a3b2f90404fULL; + +// Magic numbers for 32-bit hashing. Copied from Murmur3. +static const uint32_t c1 = 0xcc9e2d51; +static const uint32_t c2 = 0x1b873593; + +// A 32-bit to 32-bit integer hash copied from Murmur3. +static uint32_t fmix(uint32_t h) { + h ^= h >> 16; + h *= 0x85ebca6b; + h ^= h >> 13; + h *= 0xc2b2ae35; + h ^= h >> 16; + return h; +} + +static uint32_t Rotate32(uint32_t val, int shift) { + // Avoid shifting by 32: doing so yields an undefined result. + return shift == 0 ? val : ((val >> shift) | (val << (32 - shift))); +} + +#undef PERMUTE3 +#define PERMUTE3(a, b, c) \ + do { \ + std::swap(a, b); \ + std::swap(a, c); \ + } while (0) + +static uint32_t Mur(uint32_t a, uint32_t h) { + // Helper from Murmur3 for combining two 32-bit values. + a *= c1; + a = Rotate32(a, 17); + a *= c2; + h ^= a; + h = Rotate32(h, 19); + return h * 5 + 0xe6546b64; +} + +static uint32_t Hash32Len13to24(const char *s, size_t len) { + uint32_t a = Fetch32(s - 4 + (len >> 1)); + uint32_t b = Fetch32(s + 4); + uint32_t c = Fetch32(s + len - 8); + uint32_t d = Fetch32(s + (len >> 1)); + uint32_t e = Fetch32(s); + uint32_t f = Fetch32(s + len - 4); + uint32_t h = len; + + return fmix(Mur(f, Mur(e, Mur(d, Mur(c, Mur(b, Mur(a, h))))))); +} + +static uint32_t Hash32Len0to4(const char *s, size_t len) { + uint32_t b = 0; + uint32_t c = 9; + for (size_t i = 0; i < len; i++) { + signed char v = s[i]; + b = b * c1 + v; + c ^= b; + } + return fmix(Mur(b, Mur(len, c))); +} + +static uint32_t Hash32Len5to12(const char *s, size_t len) { + uint32_t a = len, b = len * 5, c = 9, d = b; + a += Fetch32(s); + b += Fetch32(s + len - 4); + c += Fetch32(s + ((len >> 1) & 4)); + return fmix(Mur(c, Mur(b, Mur(a, d)))); +} + +uint32_t CityHash32(const char *s, size_t len) { + if (len <= 24) { + return len <= 12 + ? (len <= 4 ? Hash32Len0to4(s, len) : Hash32Len5to12(s, len)) + : Hash32Len13to24(s, len); + } + + // len > 24 + uint32_t h = len, g = c1 * len, f = g; + uint32_t a0 = Rotate32(Fetch32(s + len - 4) * c1, 17) * c2; + uint32_t a1 = Rotate32(Fetch32(s + len - 8) * c1, 17) * c2; + uint32_t a2 = Rotate32(Fetch32(s + len - 16) * c1, 17) * c2; + uint32_t a3 = Rotate32(Fetch32(s + len - 12) * c1, 17) * c2; + uint32_t a4 = Rotate32(Fetch32(s + len - 20) * c1, 17) * c2; + h ^= a0; + h = Rotate32(h, 19); + h = h * 5 + 0xe6546b64; + h ^= a2; + h = Rotate32(h, 19); + h = h * 5 + 0xe6546b64; + g ^= a1; + g = Rotate32(g, 19); + g = g * 5 + 0xe6546b64; + g ^= a3; + g = Rotate32(g, 19); + g = g * 5 + 0xe6546b64; + f += a4; + f = Rotate32(f, 19); + f = f * 5 + 0xe6546b64; + size_t iters = (len - 1) / 20; + do { + uint32_t a0 = Rotate32(Fetch32(s) * c1, 17) * c2; + uint32_t a1 = Fetch32(s + 4); + uint32_t a2 = Rotate32(Fetch32(s + 8) * c1, 17) * c2; + uint32_t a3 = Rotate32(Fetch32(s + 12) * c1, 17) * c2; + uint32_t a4 = Fetch32(s + 16); + h ^= a0; + h = Rotate32(h, 18); + h = h * 5 + 0xe6546b64; + f += a1; + f = Rotate32(f, 19); + f = f * c1; + g += a2; + g = Rotate32(g, 18); + g = g * 5 + 0xe6546b64; + h ^= a3 + a1; + h = Rotate32(h, 19); + h = h * 5 + 0xe6546b64; + g ^= a4; + g = absl::gbswap_32(g) * 5; + h += a4 * 5; + h = absl::gbswap_32(h); + f += a0; + PERMUTE3(f, h, g); + s += 20; + } while (--iters != 0); + g = Rotate32(g, 11) * c1; + g = Rotate32(g, 17) * c1; + f = Rotate32(f, 11) * c1; + f = Rotate32(f, 17) * c1; + h = Rotate32(h + g, 19); + h = h * 5 + 0xe6546b64; + h = Rotate32(h, 17) * c1; + h = Rotate32(h + f, 19); + h = h * 5 + 0xe6546b64; + h = Rotate32(h, 17) * c1; + return h; +} + +// Bitwise right rotate. Normally this will compile to a single +// instruction, especially if the shift is a manifest constant. +static uint64_t Rotate(uint64_t val, int shift) { + // Avoid shifting by 64: doing so yields an undefined result. + return shift == 0 ? val : ((val >> shift) | (val << (64 - shift))); +} + +static uint64_t ShiftMix(uint64_t val) { return val ^ (val >> 47); } + +static uint64_t HashLen16(uint64_t u, uint64_t v) { + return Hash128to64(uint128(u, v)); +} + +static uint64_t HashLen16(uint64_t u, uint64_t v, uint64_t mul) { + // Murmur-inspired hashing. + uint64_t a = (u ^ v) * mul; + a ^= (a >> 47); + uint64_t b = (v ^ a) * mul; + b ^= (b >> 47); + b *= mul; + return b; +} + +static uint64_t HashLen0to16(const char *s, size_t len) { + if (len >= 8) { + uint64_t mul = k2 + len * 2; + uint64_t a = Fetch64(s) + k2; + uint64_t b = Fetch64(s + len - 8); + uint64_t c = Rotate(b, 37) * mul + a; + uint64_t d = (Rotate(a, 25) + b) * mul; + return HashLen16(c, d, mul); + } + if (len >= 4) { + uint64_t mul = k2 + len * 2; + uint64_t a = Fetch32(s); + return HashLen16(len + (a << 3), Fetch32(s + len - 4), mul); + } + if (len > 0) { + uint8_t a = s[0]; + uint8_t b = s[len >> 1]; + uint8_t c = s[len - 1]; + uint32_t y = static_cast<uint32_t>(a) + (static_cast<uint32_t>(b) << 8); + uint32_t z = len + (static_cast<uint32_t>(c) << 2); + return ShiftMix(y * k2 ^ z * k0) * k2; + } + return k2; +} + +// This probably works well for 16-byte strings as well, but it may be overkill +// in that case. +static uint64_t HashLen17to32(const char *s, size_t len) { + uint64_t mul = k2 + len * 2; + uint64_t a = Fetch64(s) * k1; + uint64_t b = Fetch64(s + 8); + uint64_t c = Fetch64(s + len - 8) * mul; + uint64_t d = Fetch64(s + len - 16) * k2; + return HashLen16(Rotate(a + b, 43) + Rotate(c, 30) + d, + a + Rotate(b + k2, 18) + c, mul); +} + +// Return a 16-byte hash for 48 bytes. Quick and dirty. +// Callers do best to use "random-looking" values for a and b. +static std::pair<uint64_t, uint64_t> WeakHashLen32WithSeeds(uint64_t w, uint64_t x, + uint64_t y, uint64_t z, + uint64_t a, uint64_t b) { + a += w; + b = Rotate(b + a + z, 21); + uint64_t c = a; + a += x; + a += y; + b += Rotate(a, 44); + return std::make_pair(a + z, b + c); +} + +// Return a 16-byte hash for s[0] ... s[31], a, and b. Quick and dirty. +static std::pair<uint64_t, uint64_t> WeakHashLen32WithSeeds(const char *s, uint64_t a, + uint64_t b) { + return WeakHashLen32WithSeeds(Fetch64(s), Fetch64(s + 8), Fetch64(s + 16), + Fetch64(s + 24), a, b); +} + +// Return an 8-byte hash for 33 to 64 bytes. +static uint64_t HashLen33to64(const char *s, size_t len) { + uint64_t mul = k2 + len * 2; + uint64_t a = Fetch64(s) * k2; + uint64_t b = Fetch64(s + 8); + uint64_t c = Fetch64(s + len - 24); + uint64_t d = Fetch64(s + len - 32); + uint64_t e = Fetch64(s + 16) * k2; + uint64_t f = Fetch64(s + 24) * 9; + uint64_t g = Fetch64(s + len - 8); + uint64_t h = Fetch64(s + len - 16) * mul; + uint64_t u = Rotate(a + g, 43) + (Rotate(b, 30) + c) * 9; + uint64_t v = ((a + g) ^ d) + f + 1; + uint64_t w = absl::gbswap_64((u + v) * mul) + h; + uint64_t x = Rotate(e + f, 42) + c; + uint64_t y = (absl::gbswap_64((v + w) * mul) + g) * mul; + uint64_t z = e + f + c; + a = absl::gbswap_64((x + z) * mul + y) + b; + b = ShiftMix((z + a) * mul + d + h) * mul; + return b + x; +} + +uint64_t CityHash64(const char *s, size_t len) { + if (len <= 32) { + if (len <= 16) { + return HashLen0to16(s, len); + } else { + return HashLen17to32(s, len); + } + } else if (len <= 64) { + return HashLen33to64(s, len); + } + + // For strings over 64 bytes we hash the end first, and then as we + // loop we keep 56 bytes of state: v, w, x, y, and z. + uint64_t x = Fetch64(s + len - 40); + uint64_t y = Fetch64(s + len - 16) + Fetch64(s + len - 56); + uint64_t z = HashLen16(Fetch64(s + len - 48) + len, Fetch64(s + len - 24)); + std::pair<uint64_t, uint64_t> v = WeakHashLen32WithSeeds(s + len - 64, len, z); + std::pair<uint64_t, uint64_t> w = WeakHashLen32WithSeeds(s + len - 32, y + k1, x); + x = x * k1 + Fetch64(s); + + // Decrease len to the nearest multiple of 64, and operate on 64-byte chunks. + len = (len - 1) & ~static_cast<size_t>(63); + do { + x = Rotate(x + y + v.first + Fetch64(s + 8), 37) * k1; + y = Rotate(y + v.second + Fetch64(s + 48), 42) * k1; + x ^= w.second; + y += v.first + Fetch64(s + 40); + z = Rotate(z + w.first, 33) * k1; + v = WeakHashLen32WithSeeds(s, v.second * k1, x + w.first); + w = WeakHashLen32WithSeeds(s + 32, z + w.second, y + Fetch64(s + 16)); + std::swap(z, x); + s += 64; + len -= 64; + } while (len != 0); + return HashLen16(HashLen16(v.first, w.first) + ShiftMix(y) * k1 + z, + HashLen16(v.second, w.second) + x); +} + +uint64_t CityHash64WithSeed(const char *s, size_t len, uint64_t seed) { + return CityHash64WithSeeds(s, len, k2, seed); +} + +uint64_t CityHash64WithSeeds(const char *s, size_t len, uint64_t seed0, + uint64_t seed1) { + return HashLen16(CityHash64(s, len) - seed0, seed1); +} + +// A subroutine for CityHash128(). Returns a decent 128-bit hash for strings +// of any length representable in signed long. Based on City and Murmur. +static uint128 CityMurmur(const char *s, size_t len, uint128 seed) { + uint64_t a = Uint128Low64(seed); + uint64_t b = Uint128High64(seed); + uint64_t c = 0; + uint64_t d = 0; + int64_t l = len - 16; + if (l <= 0) { // len <= 16 + a = ShiftMix(a * k1) * k1; + c = b * k1 + HashLen0to16(s, len); + d = ShiftMix(a + (len >= 8 ? Fetch64(s) : c)); + } else { // len > 16 + c = HashLen16(Fetch64(s + len - 8) + k1, a); + d = HashLen16(b + len, c + Fetch64(s + len - 16)); + a += d; + do { + a ^= ShiftMix(Fetch64(s) * k1) * k1; + a *= k1; + b ^= a; + c ^= ShiftMix(Fetch64(s + 8) * k1) * k1; + c *= k1; + d ^= c; + s += 16; + l -= 16; + } while (l > 0); + } + a = HashLen16(a, c); + b = HashLen16(d, b); + return uint128(a ^ b, HashLen16(b, a)); +} + +uint128 CityHash128WithSeed(const char *s, size_t len, uint128 seed) { + if (len < 128) { + return CityMurmur(s, len, seed); + } + + // We expect len >= 128 to be the common case. Keep 56 bytes of state: + // v, w, x, y, and z. + std::pair<uint64_t, uint64_t> v, w; + uint64_t x = Uint128Low64(seed); + uint64_t y = Uint128High64(seed); + uint64_t z = len * k1; + v.first = Rotate(y ^ k1, 49) * k1 + Fetch64(s); + v.second = Rotate(v.first, 42) * k1 + Fetch64(s + 8); + w.first = Rotate(y + z, 35) * k1 + x; + w.second = Rotate(x + Fetch64(s + 88), 53) * k1; + + // This is the same inner loop as CityHash64(), manually unrolled. + do { + x = Rotate(x + y + v.first + Fetch64(s + 8), 37) * k1; + y = Rotate(y + v.second + Fetch64(s + 48), 42) * k1; + x ^= w.second; + y += v.first + Fetch64(s + 40); + z = Rotate(z + w.first, 33) * k1; + v = WeakHashLen32WithSeeds(s, v.second * k1, x + w.first); + w = WeakHashLen32WithSeeds(s + 32, z + w.second, y + Fetch64(s + 16)); + std::swap(z, x); + s += 64; + x = Rotate(x + y + v.first + Fetch64(s + 8), 37) * k1; + y = Rotate(y + v.second + Fetch64(s + 48), 42) * k1; + x ^= w.second; + y += v.first + Fetch64(s + 40); + z = Rotate(z + w.first, 33) * k1; + v = WeakHashLen32WithSeeds(s, v.second * k1, x + w.first); + w = WeakHashLen32WithSeeds(s + 32, z + w.second, y + Fetch64(s + 16)); + std::swap(z, x); + s += 64; + len -= 128; + } while (ABSL_PREDICT_TRUE(len >= 128)); + x += Rotate(v.first + z, 49) * k0; + y = y * k0 + Rotate(w.second, 37); + z = z * k0 + Rotate(w.first, 27); + w.first *= 9; + v.first *= k0; + // If 0 < len < 128, hash up to 4 chunks of 32 bytes each from the end of s. + for (size_t tail_done = 0; tail_done < len;) { + tail_done += 32; + y = Rotate(x + y, 42) * k0 + v.second; + w.first += Fetch64(s + len - tail_done + 16); + x = x * k0 + w.first; + z += w.second + Fetch64(s + len - tail_done); + w.second += v.first; + v = WeakHashLen32WithSeeds(s + len - tail_done, v.first + z, v.second); + v.first *= k0; + } + // At this point our 56 bytes of state should contain more than + // enough information for a strong 128-bit hash. We use two + // different 56-byte-to-8-byte hashes to get a 16-byte final result. + x = HashLen16(x, v.first); + y = HashLen16(y + z, w.first); + return uint128(HashLen16(x + v.second, w.second) + y, + HashLen16(x + w.second, y + v.second)); +} + +uint128 CityHash128(const char *s, size_t len) { + return len >= 16 + ? CityHash128WithSeed(s + 16, len - 16, + uint128(Fetch64(s), Fetch64(s + 8) + k0)) + : CityHash128WithSeed(s, len, uint128(k0, k1)); +} +} // namespace hash_internal +} // namespace absl + +#ifdef __SSE4_2__ +#include <nmmintrin.h> +#include "absl/hash/internal/city_crc.h" + +namespace absl { +namespace hash_internal { + +// Requires len >= 240. +static void CityHashCrc256Long(const char *s, size_t len, uint32_t seed, + uint64_t *result) { + uint64_t a = Fetch64(s + 56) + k0; + uint64_t b = Fetch64(s + 96) + k0; + uint64_t c = result[0] = HashLen16(b, len); + uint64_t d = result[1] = Fetch64(s + 120) * k0 + len; + uint64_t e = Fetch64(s + 184) + seed; + uint64_t f = 0; + uint64_t g = 0; + uint64_t h = c + d; + uint64_t x = seed; + uint64_t y = 0; + uint64_t z = 0; + + // 240 bytes of input per iter. + size_t iters = len / 240; + len -= iters * 240; + do { +#undef CHUNK +#define CHUNK(r) \ + PERMUTE3(x, z, y); \ + b += Fetch64(s); \ + c += Fetch64(s + 8); \ + d += Fetch64(s + 16); \ + e += Fetch64(s + 24); \ + f += Fetch64(s + 32); \ + a += b; \ + h += f; \ + b += c; \ + f += d; \ + g += e; \ + e += z; \ + g += x; \ + z = _mm_crc32_u64(z, b + g); \ + y = _mm_crc32_u64(y, e + h); \ + x = _mm_crc32_u64(x, f + a); \ + e = Rotate(e, r); \ + c += e; \ + s += 40 + + CHUNK(0); + PERMUTE3(a, h, c); + CHUNK(33); + PERMUTE3(a, h, f); + CHUNK(0); + PERMUTE3(b, h, f); + CHUNK(42); + PERMUTE3(b, h, d); + CHUNK(0); + PERMUTE3(b, h, e); + CHUNK(33); + PERMUTE3(a, h, e); + } while (--iters > 0); + + while (len >= 40) { + CHUNK(29); + e ^= Rotate(a, 20); + h += Rotate(b, 30); + g ^= Rotate(c, 40); + f += Rotate(d, 34); + PERMUTE3(c, h, g); + len -= 40; + } + if (len > 0) { + s = s + len - 40; + CHUNK(33); + e ^= Rotate(a, 43); + h += Rotate(b, 42); + g ^= Rotate(c, 41); + f += Rotate(d, 40); + } + result[0] ^= h; + result[1] ^= g; + g += h; + a = HashLen16(a, g + z); + x += y << 32; + b += x; + c = HashLen16(c, z) + h; + d = HashLen16(d, e + result[0]); + g += e; + h += HashLen16(x, f); + e = HashLen16(a, d) + g; + z = HashLen16(b, c) + a; + y = HashLen16(g, h) + c; + result[0] = e + z + y + x; + a = ShiftMix((a + y) * k0) * k0 + b; + result[1] += a + result[0]; + a = ShiftMix(a * k0) * k0 + c; + result[2] = a + result[1]; + a = ShiftMix((a + e) * k0) * k0; + result[3] = a + result[2]; +} + +// Requires len < 240. +static void CityHashCrc256Short(const char *s, size_t len, uint64_t *result) { + char buf[240]; + memcpy(buf, s, len); + memset(buf + len, 0, 240 - len); + CityHashCrc256Long(buf, 240, ~static_cast<uint32_t>(len), result); +} + +void CityHashCrc256(const char *s, size_t len, uint64_t *result) { + if (ABSL_PREDICT_TRUE(len >= 240)) { + CityHashCrc256Long(s, len, 0, result); + } else { + CityHashCrc256Short(s, len, result); + } +} + +uint128 CityHashCrc128WithSeed(const char *s, size_t len, uint128 seed) { + if (len <= 900) { + return CityHash128WithSeed(s, len, seed); + } else { + uint64_t result[4]; + CityHashCrc256(s, len, result); + uint64_t u = Uint128High64(seed) + result[0]; + uint64_t v = Uint128Low64(seed) + result[1]; + return uint128(HashLen16(u, v + result[2]), + HashLen16(Rotate(v, 32), u * k0 + result[3])); + } +} + +uint128 CityHashCrc128(const char *s, size_t len) { + if (len <= 900) { + return CityHash128(s, len); + } else { + uint64_t result[4]; + CityHashCrc256(s, len, result); + return uint128(result[2], result[3]); + } +} + +} // namespace hash_internal +} // namespace absl + +#endif |