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42 lines
1.4 KiB
Nim
42 lines
1.4 KiB
Nim
#
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#
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# Nim's Runtime Library
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# (c) Copyright 2012 Andreas Rumpf
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#
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# See the file "copying.txt", included in this
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# distribution, for details about the copyright.
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#
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# set handling
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type
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NimSet = array[0..4*2048-1, uint8]
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# bitops can't be imported here, therefore the code duplication.
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proc countBits32(n: uint32): int {.compilerproc.} =
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# generic formula is from: https://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
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var v = uint32(n)
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v = v - ((v shr 1'u32) and 0x55555555'u32)
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v = (v and 0x33333333'u32) + ((v shr 2'u32) and 0x33333333'u32)
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result = (((v + (v shr 4'u32) and 0xF0F0F0F'u32) * 0x1010101'u32) shr 24'u32).int
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proc countBits64(n: uint64): int {.compilerproc, inline.} =
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# generic formula is from: https://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
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var v = uint64(n)
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v = v - ((v shr 1'u64) and 0x5555555555555555'u64)
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v = (v and 0x3333333333333333'u64) + ((v shr 2'u64) and 0x3333333333333333'u64)
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v = (v + (v shr 4'u64) and 0x0F0F0F0F0F0F0F0F'u64)
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result = ((v * 0x0101010101010101'u64) shr 56'u64).int
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proc cardSet(s: NimSet, len: int): int {.compilerproc, inline.} =
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var i = 0
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when defined(x86) or defined(amd64):
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while i < len - 8:
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inc(result, countBits64((cast[ptr uint64](s[i].unsafeAddr))[]))
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inc(i, 8)
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while i < len:
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inc(result, countBits32(uint32(s[i])))
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inc(i, 1)
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