Created
June 9, 2018 22:51
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tabulation hashing
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| import std.stdio; | |
| import std.datetime; | |
| @safe: | |
| private immutable ulong[256][8] tables_; | |
| static this() | |
| { | |
| import std.random : unpredictableSeed; | |
| foreach (ref table; tables_) { | |
| foreach (ref b; table) { | |
| b = unpredictableSeed(); | |
| } | |
| } | |
| } | |
| ulong hash(in ulong key) @trusted @nogc pure nothrow | |
| { | |
| /** | |
| * Trusted operation: taking address of parameter | |
| */ | |
| const bytes = (cast(const(ubyte)*) &key)[0 .. ulong.sizeof / ubyte.sizeof]; | |
| ulong h = 0; | |
| static foreach (i; 0 .. tables_.length) { | |
| h ^= tables_[i][bytes[i]]; | |
| } | |
| return h; | |
| } | |
| void main() | |
| { | |
| immutable start = Clock.currTime; | |
| foreach (i; 0 .. 100_000) { | |
| hash(i); | |
| } | |
| immutable delta = Clock.currTime - start; | |
| writeln(delta); | |
| } |
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