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getLSBIndex: Replace PoT lookup table with Math.clz32 #42

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getLSBIndex: Replace PoT lookup table with Math.clz32 #42

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41 changes: 1 addition & 40 deletions utilities.ts
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Original file line number Diff line number Diff line change
@@ -1,41 +1,3 @@
/**
* Lookup table for powers of 2
*/
export const log2: Record<number, number> = {
1: 0,
2: 1,
4: 2,
8: 3,
16: 4,
32: 5,
64: 6,
128: 7,
256: 8,
512: 9,
1024: 10,
2048: 11,
4096: 12,
8192: 13,
16384: 14,
32768: 15,
65536: 16,
131072: 17,
262144: 18,
524288: 19,
1048576: 20,
2097152: 21,
4194304: 22,
8388608: 23,
16777216: 24,
33554432: 25,
67108864: 26,
134217728: 27,
268435456: 28,
536870912: 29,
1073741824: 30,
2147483648: 31,
};

/**
* Counts set bits in a given number.
*
Expand All @@ -55,8 +17,7 @@ export function popCount32(value: number): number {
* @return the index of LSB
*/
export function getLSBIndex(value: number): number {
if (value === 2147483648) return 31;
return log2[value & -value];
return 31 - Math.clz32(value & -value);
}

/**
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