78 lines
2.0 KiB
C#
78 lines
2.0 KiB
C#
using System.Runtime.CompilerServices;
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namespace PerfectNumbers.Core;
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public static class UIntExtensions
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{
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private static readonly byte[] Mod6Lookup = { 0, 3, 4, 1, 2, 5 };
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static uint Mod3(this uint value)
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{
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uint quotient = (uint)(((ulong)value * 0xAAAAAAABUL) >> 33);
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return value - quotient * 3U;
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static uint Mod5(this uint value)
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{
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uint quotient = (uint)(((ulong)value * 0xCCCCCCCDUL) >> 34);
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return value - quotient * 5U;
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static uint Mod6(this uint value)
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{
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uint key = (value.Mod3() << 1) | (value & 1U);
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return Mod6Lookup[(int)key];
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static uint Mod7(this uint value)
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{
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uint remainder = 0U;
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uint temp = value;
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while (temp != 0U)
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{
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remainder += temp & 7U;
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temp >>= 3;
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if (remainder >= 7U)
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{
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remainder -= 7U;
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}
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}
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return remainder >= 7U ? remainder - 7U : remainder;
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static uint Mod8(this uint value) => value & 7U;
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static uint Mod10(this uint value)
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{
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return value - (uint)(((ulong)value * 0xCCCCCCCDUL) >> 35) * 10U;
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static uint Mod11(this uint value)
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{
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uint remainder = 0U;
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uint temp = value;
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while (temp != 0U)
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{
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remainder += temp & 1023U;
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temp >>= 10;
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remainder -= 11U * (remainder / 11U);
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}
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return remainder;
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static uint Mod128(this uint value) => value & 127U;
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}
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