130 lines
3.3 KiB
V
130 lines
3.3 KiB
V
// Copyright (c) 2019-2021 Alexander Medvednikov. All rights reserved.
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// Use of this source code is governed by an MIT license
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// that can be found in the LICENSE file.
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//
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// this is an implementation of wyhash v4
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// from https://github.com/wangyi-fudan/wyhash
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//
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// TODO: use u128 once implemented
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// currently the C version performs slightly better
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// because it uses 128 bit int when available and
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// branch prediction hints. the C version will be
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// removed once the perfomance is matched.
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// you can test performance by running:
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// `v run cmd/tools/bench/wyhash.v`
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// try running with and without the `-prod` flag
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module hash
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const (
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wyp0 = u64(0xa0761d6478bd642f)
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wyp1 = u64(0xe7037ed1a0b428db)
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wyp2 = u64(0x8ebc6af09c88c6e3)
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wyp3 = u64(0x589965cc75374cc3)
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wyp4 = u64(0x1d8e4e27c47d124f)
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)
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[inline]
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pub fn sum64_string(key string, seed u64) u64 {
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return wyhash64(key.str, u64(key.len), seed)
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}
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[inline]
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pub fn sum64(key []byte, seed u64) u64 {
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return wyhash64(byteptr(key.data), u64(key.len), seed)
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}
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[inline]
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fn wyhash64(key byteptr, len u64, seed_ u64) u64 {
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if len == 0 {
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return 0
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}
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mut p := key
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mut seed := seed_
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mut i := len & 63
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seed = unsafe{match i {
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0...3 {
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wymum(wyr3(p, i) ^ seed ^ wyp0, seed ^ wyp1)
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}
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4...8 {
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wymum(wyr4(p) ^ seed ^ wyp0, wyr4(p + i - 4) ^ seed ^ wyp1)
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}
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9...16 {
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wymum(wyr8(p) ^ seed ^ wyp0, wyr8(p + i - 8) ^ seed ^ wyp1)
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}
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17...24 {
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wymum(wyr8(p) ^ seed ^ wyp0, wyr8(p + 8) ^ seed ^ wyp1) ^ wymum(wyr8(p + i - 8) ^ seed ^ wyp2, seed ^ wyp3)
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}
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25...32 {
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wymum(wyr8(p) ^ seed ^ wyp0, wyr8(p + 8) ^ seed ^ wyp1) ^ wymum(wyr8(p + 16) ^ seed ^ wyp2, wyr8(p + i - 8) ^ seed ^ wyp3)
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}
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else {
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wymum(wyr8(p) ^ seed ^ wyp0, wyr8(p + 8) ^ seed ^ wyp1) ^ wymum(wyr8(p + 16) ^ seed ^ wyp2, wyr8(p + 24) ^ seed ^ wyp3) ^ wymum(wyr8(p + i - 32) ^ seed ^ wyp1, wyr8(p + i - 24) ^ seed ^ wyp2) ^ wymum(wyr8(p + i - 16) ^ seed ^ wyp3, wyr8(p + i - 8) ^ seed ^ wyp0)
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}
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}}
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if i == len {
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return wymum(seed, len ^ wyp4)
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}
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mut see1 := seed
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mut see2 := seed
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mut see3 := seed
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unsafe {
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p = p + i
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for i = len - i; i >= 64; i -= 64 {
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seed = wymum(wyr8(p) ^ seed ^ wyp0, wyr8(p + 8) ^ seed ^ wyp1)
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see1 = wymum(wyr8(p + 16) ^ see1 ^ wyp2, wyr8(p + 24) ^ see1 ^ wyp3)
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see2 = wymum(wyr8(p + 32) ^ see2 ^ wyp1, wyr8(p + 40) ^ see2 ^ wyp2)
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see3 = wymum(wyr8(p + 48) ^ see3 ^ wyp3, wyr8(p + 56) ^ see3 ^ wyp0)
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p = p + 64
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}
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}
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return wymum(seed ^ see1 ^ see2, see3 ^ len ^ wyp4)
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}
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[inline]
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fn wyrotr(v u64, k u32) u64 {
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return (v>>k) | (v<<(64 - k))
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}
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[inline]
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pub fn wymum(a u64, b u64) u64 {
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/*
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mut r := u128(a)
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r = r*b
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return (r>>64)^r
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*/
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mask32 := u32(4294967295)
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x0 := a & mask32
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x1 := a>>32
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y0 := b & mask32
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y1 := b>>32
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w0 := x0 * y0
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t := x1 * y0 + (w0>>32)
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mut w1 := t & mask32
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w2 := t>>32
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w1 += x0 * y1
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hi := x1 * y1 + w2 + (w1>>32)
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lo := a * b
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return hi ^ lo
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}
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[inline]
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fn wyr3(p byteptr, k u64) u64 {
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unsafe {
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return (u64(p[0])<<16) | (u64(p[k>>1])<<8) | u64(p[k - 1])
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}
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}
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[inline]
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fn wyr4(p byteptr) u64 {
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unsafe {
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return u32(p[0]) | (u32(p[1])<<u32(8)) | (u32(p[2])<<u32(16)) | (u32(p[3])<<u32(24))
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}
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}
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[inline]
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fn wyr8(p byteptr) u64 {
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unsafe {
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return u64(p[0]) | (u64(p[1])<<8) | (u64(p[2])<<16) | (u64(p[3])<<24) | (u64(p[4])<<32) | (u64(p[5])<<40) | (u64(p[6])<<48) | (u64(p[7])<<56)
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}
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}
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