73 lines
1.7 KiB
V
73 lines
1.7 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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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 &byte, 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 &byte) 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 &byte) 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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