Use word-wise hash instead of FNV-1a for arrays of word-aligned scalars
Also special case int-aligned scalars on 64-bit machines. On a 64-bit machine hashing an array of pointers is now ~5.95x faster with LDC2 and ~8.54x faster with DMD, and hashing an array of ints is ~3.34x faster with LDC2 and ~8.12x faster with DMD.
This commit is contained in:
Nathan Sashihara
parent
0bef2ef76d
commit
a786bdbec5
@ -18,7 +18,7 @@ import tanya.meta.trait;
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import tanya.range.primitive;
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version (unittest) import tanya.test.stub;
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private struct FNV
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private struct Hasher
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{
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static if (size_t.sizeof == 4)
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{
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@ -50,11 +50,33 @@ private struct FNV
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}
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else static if (isScalarType!T || isPointer!T)
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{
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(() @trusted => add((cast(const ubyte*) &key)[0 .. T.sizeof]))();
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// Treat as an array of words
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static if (T.sizeof % size_t.sizeof == 0
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&& T.alignof >= size_t.alignof)
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alias CastT = size_t;
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// (64-bit or 128-bit) Treat as an array of ints
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else static if (T.sizeof % uint.sizeof == 0
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&& T.alignof >= uint.alignof)
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alias CastT = uint;
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// Treat as an array of bytes
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else
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alias CastT = ubyte;
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add((() @trusted => (cast(const CastT*) &key)[0 .. T.sizeof / CastT.sizeof])());
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}
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else static if (isArray!T && isScalarType!(ElementType!T))
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{
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add(cast(const ubyte[]) key);
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// Treat as an array of words
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static if (ElementType!T.sizeof % size_t.sizeof == 0
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&& ElementType!T.alignof >= size_t.alignof)
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alias CastT = size_t;
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// (64-bit or 128-bit) Treat as an array of ints
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else static if (ElementType!T.sizeof % uint.sizeof == 0
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&& ElementType!T.alignof >= uint.alignof)
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alias CastT = uint;
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// Treat as an array of bytes
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else
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alias CastT = ubyte;
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add(cast(const CastT[]) key);
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}
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else static if (is(T == typeof(null)))
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{
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@ -73,13 +95,166 @@ private struct FNV
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}
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}
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void add(const ubyte[] key) @nogc nothrow pure @safe
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void add(scope const ubyte[] key) @nogc nothrow pure @safe
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{
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// FNV-1a
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foreach (c; key)
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{
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this.hash = (this.hash ^ c) * prime;
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}
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}
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void add(scope const size_t[] key) @nogc nothrow pure @safe
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{
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static if (size_t.sizeof == 4)
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{
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// Partial MurmurHash3_x86_32 (no finalization)
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enum uint c1 = 0xcc9e2d51;
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enum uint c2 = 0x1b873593;
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alias h1 = hash;
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foreach (x; key)
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{
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auto k1 = x * c1;
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k1 = (k1 << 15) | (k1 >> (32 - 15));
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k1 *= c2;
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h1 ^= k1;
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h1 = (h1 << 13) | (h1 >> (32 - 13));
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h1 = h1 * 5 + 0xe6546b64;
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}
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}
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else static if (size_t.sizeof == 8)
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{
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// Partial 64-bit MurmurHash64A (no finalization)
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alias h = hash;
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enum ulong m = 0xc6a4a7935bd1e995UL;
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foreach (x; key)
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{
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auto k = x * m;
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k ^= k >>> 47;
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k *= m;
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h ^= k;
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h *= m;
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}
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}
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else static if (size_t.sizeof == 16)
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{
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// Partial MurmurHash3_x64_128 (no finalization)
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// treating each size_t as a pair of ulong.
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ulong h1 = cast(ulong) hash;
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ulong h2 = cast(ulong) (hash >> 64);
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enum ulong c1 = 0x87c37b91114253d5UL;
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enum ulong c2 = 0x4cf5ad432745937fUL;
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foreach (x; key)
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{
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auto k1 = cast(ulong) x;
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auto k2 = cast(ulong) (x >> 64);
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k1 *= c1; k1 = (k1 << 32) | (k1 >> (64 - 31)); k1 *= c2; h1 ^= k1;
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h1 = (h1 << 27) | (h1 >> (64 - 27)); h1 += h2; h1 = h1*5+0x52dce729;
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k2 *= c2; k2 = (k2 << 33) | (k2 >> (64 - 33)); k2 *= c1; h2 ^= k2;
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h2 = (h2 << 31) | (h2 >> (64 - 31)); h2 += h1; h2 = h2*5+0x38495ab5;
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}
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hash = cast(size_t) h1 + ((cast(size_t) h2) << 64);
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}
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else
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{
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static assert(0, "Hash length must be either 32, 64, or 128 bits.");
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}
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}
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static if (size_t.sizeof != uint.sizeof)
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void add(scope const uint[] key) @nogc nothrow pure @trusted
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{
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static if (size_t.sizeof == 8)
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{
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// Partial 32-bit MurmurHash64B (no finalization)
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enum uint m = 0x5bd1e995;
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enum r = 24;
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uint h1 = cast(uint) hash;
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uint h2 = cast(uint) (hash >> 32);
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const(uint)* data = key.ptr;
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auto len = key.length;
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for (; len >= 2; data += 2, len -= 2)
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{
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uint k1 = data[0];
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k1 *= m; k1 ^= k1 >> r; k1 *= m;
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h1 *= m; h1 ^= k1;
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uint k2 = data[1];
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k2 *= m; k2 ^= k2 >> r; k2 *= m;
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h2 *= m; h2 ^= k2;
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}
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if (len)
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{
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uint k1 = data[0];
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k1 *= m; k1 ^= k1 >> r; k1 *= m;
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h1 *= m; h1 ^= k1;
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}
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hash = cast(ulong) h1 + ((cast(ulong) h2) << 32);
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}
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else static if (size_t.sizeof == 16)
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{
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// Partial MurmurHash3_x86_128 (no finalization)
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enum uint c1 = 0x239b961b;
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enum uint c2 = 0xab0e9789;
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enum uint c3 = 0x38b34ae5;
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enum uint c4 = 0xa1e38b93;
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uint h1 = cast(uint) hash;
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uint h2 = cast(uint) (hash >> 32);
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uint h3 = cast(uint) (hash >> 64);
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uint h4 = cast(uint) (hash >> 96);
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const(uint)* data = key.ptr;
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auto len = key.length;
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for (; len >= 4; data += 4, len -= 4)
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{
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uint k1 = data[0];
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uint k2 = data[1];
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uint k3 = data[2];
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uint k4 = data[3];
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h1 = (h1 << 19) | (h1 >> (32 - 19)); h1 += h2; h1 = h1*5+0x561ccd1b;
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k2 *= c2; k2 = (k2 << 16) | (k2 >> (32 - 16)); k2 *= c3; h2 ^= k2;
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h2 = (h2 << 17) | (h2 >> (32 - 17)); h2 += h3; h2 = h2*5+0x0bcaa747;
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k3 *= c3; k3 = (k3 << 17) | (k3 >> (32 - 17)); k3 *= c4; h3 ^= k3;
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h3 = (h3 << 15) | (h3 >> (32 - 15)); h3 += h4; h3 = h3*5+0x96cd1c35;
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k4 *= c4; k4 = (k4 << 18) | (k4 >> (32 - 18)); k4 *= c1; h4 ^= k4;
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h4 = (h4 << 13) | (h4 >> (32 - 13)); h4 += h1; h4 = h4*5+0x32ac3b17;
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}
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uint k1, k2, k3;
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switch (len) // 0, 1, 2, 3
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{
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case 3:
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k3 = data[2];
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k3 *= c3; k3 = (k3 << 17) | (k3 >> (32 - 17)); k3 *= c4; h3 ^= k3;
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goto case;
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case 2:
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k2 = data[1];
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k2 *= c2; k2 = (k2 << 16) | (k2 >> (32 - 16)); k2 *= c3; h2 ^= k2;
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goto case;
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case 1:
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k1 = data[0];
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k1 *= c1; k1 = (k1 << 15) | (k1 >> (32 - 15)); k1 *= c2; h1 ^= k1;
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break;
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}
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hash = cast(size_t) h1 +
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((cast(size_t) h2) << 32) +
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((cast(size_t) h3) << 64) +
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((cast(size_t) h4) << 96);
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}
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else
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{
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static assert(0, "Hash length must be either 32, 64, or 128 bits.");
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}
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}
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}
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/**
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@ -98,7 +273,8 @@ private struct FNV
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* For pointers and for scalar types implicitly convertible to `size_t` this
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* is an identity operation (i.e. the value is cast to `size_t` and returned
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* unaltered). Integer types wider than `size_t` are XOR folded down to
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* `size_t`. Other scalar types use the FNV-1a (Fowler-Noll-Vo) hash function.
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* `size_t`. Other scalar types use an architecture-dependent hash function
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* based on their width and alignment.
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* If the type provides a `toHash`-function, only `toHash()` is called and its
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* result is returned.
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*
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@ -134,9 +310,9 @@ size_t hash(T)(auto ref T key)
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}
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else
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{
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FNV fnv;
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fnv(key);
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return fnv.hash;
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Hasher hasher;
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hasher(key);
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return hasher.hash;
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}
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}
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@ -199,12 +375,12 @@ version (unittest)
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static if (size_t.sizeof == 4) @nogc nothrow pure @safe unittest
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{
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assert(hash(HashRange()) == 0x6222e842U);
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assert(hash(ToHashRange()) == 1268118805U);
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assert(hash(ToHashRange()) == 3371162643U);
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}
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static if (size_t.sizeof == 8) @nogc nothrow pure @safe unittest
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{
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assert(hash(HashRange()) == 0x08985907b541d342UL);
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assert(hash(ToHashRange()) == 12161962213042174405UL);
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assert(hash(ToHashRange()) == 2072958611659694473);
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}
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static if (size_t.sizeof == 4) @nogc nothrow pure @system unittest
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