/usr/share/gocode/src/github.com/retailnext/hllpp/dense.go is in golang-github-retailnext-hllpp-dev 1.0.0+git20170901.6e8b6d3-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 | // Copyright (c) 2015, RetailNext, Inc.
// All rights reserved.
package hllpp
import "sort"
// create a mask of numOnes 1's, shifted left shift bits
func mask(numOnes, shift uint32) uint32 {
return ((1 << numOnes) - 1) << shift
}
func setRegister(data []byte, bitsPerRegister, idx uint32, rho uint8) {
bitIdx := idx * bitsPerRegister
byteOffset := bitIdx / 8
bitOffset := bitIdx % 8
if 8-bitOffset >= bitsPerRegister {
// can all fit in first byte
leftShift := 8 - bitsPerRegister - bitOffset
// clear existing register value
data[byteOffset] &= ^byte(mask(bitsPerRegister, leftShift))
data[byteOffset] |= rho << leftShift
} else {
// spread over two bytes
numBitsInFirstByte := bitsPerRegister - (8 - bitOffset)
data[byteOffset] &= ^byte(mask(8-bitOffset, 0))
data[byteOffset] |= rho >> numBitsInFirstByte
data[byteOffset+1] &= ^byte(mask(numBitsInFirstByte, 8-numBitsInFirstByte))
data[byteOffset+1] |= rho << (8 - numBitsInFirstByte)
}
}
func getRegister(data []byte, bitsPerRegister, idx uint32) uint8 {
bitIdx := idx * bitsPerRegister
byteOffset := bitIdx / 8
bitOffset := bitIdx % 8
if 8-bitOffset >= bitsPerRegister {
// all fit in first byte
return (data[byteOffset] >> (8 - bitOffset - bitsPerRegister)) & byte(mask(bitsPerRegister, 0))
} else {
// spread over two bytes
numBitsInFirstByte := bitsPerRegister - (8 - bitOffset)
rho := data[byteOffset] << numBitsInFirstByte
rho |= data[byteOffset+1] >> (8 - numBitsInFirstByte)
return rho & byte(mask(bitsPerRegister, 0))
}
}
func alpha(m uint32) float64 {
switch m {
case 16:
return 0.673
case 32:
return 0.697
case 64:
return 0.709
default:
return 0.7213 / (1 + 1.079/float64(m))
}
}
func (h *HLLPP) estimateBias(e float64) float64 {
estimates := rawEstimateData[h.p-4]
biases := biasData[h.p-4]
index := sort.SearchFloat64s(estimates, e)
if index == 0 {
return biases[0]
} else if index == len(estimates) {
return biases[len(biases)-1]
}
e1, e2 := estimates[index-1], estimates[index]
b1, b2 := biases[index-1], biases[index]
r := (e - e1) / (e2 - e1)
return b1*(1-r) + b2*r
}
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