57 lines
958 B
Go
57 lines
958 B
Go
package nip45
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import "math"
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const two32 = 1 << 32
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// Extract bits from uint64 using LSB 0 numbering, including lo.
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func eb(bits uint64, hi uint8, lo uint8) uint64 {
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m := uint64(((1 << (hi - lo)) - 1) << lo)
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return (bits & m) >> lo
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}
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func linearCounting(m uint32, v uint32) float64 {
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fm := float64(m)
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return fm * math.Log(fm/float64(v))
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}
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func clz64(x uint64) uint8 {
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var c uint8
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for m := uint64(1 << 63); m&x == 0 && m != 0; m >>= 1 {
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c++
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}
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return c
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}
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func countZeros(s []uint8) uint32 {
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var c uint32
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for _, v := range s {
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if v == 0 {
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c++
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}
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}
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return c
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}
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func calculateEstimate(s []uint8) float64 {
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sum := 0.0
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for _, val := range s {
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sum += 1.0 / float64(uint64(1)<<val)
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}
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m := uint32(len(s))
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fm := float64(m)
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return alpha(m) * fm * fm / sum
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}
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func alpha(m uint32) float64 {
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if m == 16 {
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return 0.673
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} else if m == 32 {
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return 0.697
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} else if m == 64 {
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return 0.709
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}
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return 0.7213 / (1 + 1.079/float64(m))
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}
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