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TPAQPredictor.go
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TPAQPredictor.go
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/*
Copyright 2011-2017 Frederic Langlet
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
you may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package entropy
import (
"math/bits"
kanzi "github.com/flanglet/kanzi-go"
)
const (
_TPAQ_MAX_LENGTH = 88
_TPAQ_BUFFER_SIZE = 64 * 1024 * 1024
_TPAQ_HASH_SIZE = 16 * 1024 * 1024
_TPAQ_MASK_BUFFER = _TPAQ_BUFFER_SIZE - 1
_TPAQ_MASK_80808080 = int32(-2139062144) // 0x80808080
_TPAQ_MASK_F0F0F000 = int32(-252645376) // 0xF0F0F000
_TPAQ_MASK_4F4FFFFF = int32(1330642943) // 0x4F4FFFFF
_TPAQ_MASK_FFFF0000 = int32(-65536) // 0xFFFF0000
_TPAQ_HASH = int32(0x7FEB352D)
_TPAQ_BEGIN_LEARN_RATE = 60 << 7
_TPAQ_END_LEARN_RATE = 11 << 7
)
// States represent a bit history within some context.
// State 0 is the starting state (no bits seen).
// States 1-30 represent all possible sequences of 1-4 bits.
// States 31-252 represent a pair of counts, (n0,n1), the number
// of 0 and 1 bits respectively. If n0+n1 < 16 then there are
// two states for each pair, depending on if a 0 or 1 was the last
// bit seen.
// If n0 and n1 are too large, then there is no state to represent this
// pair, so another state with about the same ratio of n0/n1 is substituted.
// Also, when a bit is observed and the count of the opposite bit is large,
// then part of this count is discarded to favor newer data over old.
var _TPAQ_STATE_TRANSITIONS = [][]uint8{
// Bit 0
{
1, 3, 143, 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, 47, 54, 55, 56, 57, 58, 59, 60,
61, 62, 63, 64, 65, 66, 67, 68, 69, 6,
71, 71, 71, 61, 75, 56, 77, 78, 77, 80,
81, 82, 83, 84, 85, 86, 87, 88, 77, 90,
91, 92, 80, 94, 95, 96, 97, 98, 99, 90,
101, 94, 103, 101, 102, 104, 107, 104, 105, 108,
111, 112, 113, 114, 115, 116, 92, 118, 94, 103,
119, 122, 123, 94, 113, 126, 113, 128, 129, 114,
131, 132, 112, 134, 111, 134, 110, 134, 134, 128,
128, 142, 143, 115, 113, 142, 128, 148, 149, 79,
148, 142, 148, 150, 155, 149, 157, 149, 159, 149,
131, 101, 98, 115, 114, 91, 79, 58, 1, 170,
129, 128, 110, 174, 128, 176, 129, 174, 179, 174,
176, 141, 157, 179, 185, 157, 187, 188, 168, 151,
191, 192, 188, 187, 172, 175, 170, 152, 185, 170,
176, 170, 203, 148, 185, 203, 185, 192, 209, 188,
211, 192, 213, 214, 188, 216, 168, 84, 54, 54,
221, 54, 55, 85, 69, 63, 56, 86, 58, 230,
231, 57, 229, 56, 224, 54, 54, 66, 58, 54,
61, 57, 222, 78, 85, 82, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0,
},
// Bit 1
{
2, 163, 169, 163, 165, 89, 245, 217, 245, 245,
233, 244, 227, 74, 221, 221, 218, 226, 243, 218,
238, 242, 74, 238, 241, 240, 239, 224, 225, 221,
232, 72, 224, 228, 223, 225, 238, 73, 167, 76,
237, 234, 231, 72, 31, 63, 225, 237, 236, 235,
53, 234, 53, 234, 229, 219, 229, 233, 232, 228,
226, 72, 74, 222, 75, 220, 167, 57, 218, 70,
168, 72, 73, 74, 217, 76, 167, 79, 79, 166,
162, 162, 162, 162, 165, 89, 89, 165, 89, 162,
93, 93, 93, 161, 100, 93, 93, 93, 93, 93,
161, 102, 120, 104, 105, 106, 108, 106, 109, 110,
160, 134, 108, 108, 126, 117, 117, 121, 119, 120,
107, 124, 117, 117, 125, 127, 124, 139, 130, 124,
133, 109, 110, 135, 110, 136, 137, 138, 127, 140,
141, 145, 144, 124, 125, 146, 147, 151, 125, 150,
127, 152, 153, 154, 156, 139, 158, 139, 156, 139,
130, 117, 163, 164, 141, 163, 147, 2, 2, 199,
171, 172, 173, 177, 175, 171, 171, 178, 180, 172,
181, 182, 183, 184, 186, 178, 189, 181, 181, 190,
193, 182, 182, 194, 195, 196, 197, 198, 169, 200,
201, 202, 204, 180, 205, 206, 207, 208, 210, 194,
212, 184, 215, 193, 184, 208, 193, 163, 219, 168,
94, 217, 223, 224, 225, 76, 227, 217, 229, 219,
79, 86, 165, 217, 214, 225, 216, 216, 234, 75,
214, 237, 74, 74, 163, 217, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0,
},
}
var _TPAQ_STATE_MAP = []int32{
-31, -400, 406, -547, -642, -743, -827, -901,
-901, -974, -945, -955, -1060, -1031, -1044, -956,
-994, -1035, -1147, -1069, -1111, -1145, -1096, -1084,
-1171, -1199, -1062, -1498, -1199, -1199, -1328, -1405,
-1275, -1248, -1167, -1448, -1441, -1199, -1357, -1160,
-1437, -1428, -1238, -1343, -1526, -1331, -1443, -2047,
-2047, -2044, -2047, -2047, -2047, -232, -414, -573,
-517, -768, -627, -666, -644, -740, -721, -829,
-770, -963, -863, -1099, -811, -830, -277, -1036,
-286, -218, -42, -411, 141, -1014, -1028, -226,
-469, -540, -573, -581, -594, -610, -628, -711,
-670, -144, -408, -485, -464, -173, -221, -310,
-335, -375, -324, -413, -99, -179, -105, -150,
-63, -9, 56, 83, 119, 144, 198, 118,
-42, -96, -188, -285, -376, 107, -138, 38,
-82, 186, -114, -190, 200, 327, 65, 406,
108, -95, 308, 171, -18, 343, 135, 398,
415, 464, 514, 494, 508, 519, 92, -123,
343, 575, 585, 516, -7, -156, 209, 574,
613, 621, 670, 107, 989, 210, 961, 246,
254, -12, -108, 97, 281, -143, 41, 173,
-209, 583, -55, 250, 354, 558, 43, 274,
14, 488, 545, 84, 528, 519, 587, 634,
663, 95, 700, 94, -184, 730, 742, 162,
-10, 708, 692, 773, 707, 855, 811, 703,
790, 871, 806, 9, 867, 840, 990, 1023,
1409, 194, 1397, 183, 1462, 178, -23, 1403,
247, 172, 1, -32, -170, 72, -508, -46,
-365, -26, -146, 101, -18, -163, -422, -461,
-146, -69, -78, -319, -334, -232, -99, 0,
47, -74, 0, -452, 14, -57, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
}
func hashTPAQ(x, y int32) int32 {
h := x*_TPAQ_HASH ^ y*_TPAQ_HASH
return h>>1 ^ h>>9 ^ x>>2 ^ y>>3 ^ _TPAQ_HASH
}
// TPAQPredictor bit predictor for binary entropy codecs.
// It uses a mixer to combine initial predictions derived for several
// local contexts and a secondary symbol estimation to improve the
// prediction from the mixer.
// It is a heavily modified version of Tangelo 2.4 (by Jan Ondrus), itself
// derived from PAQ8 (by Matt Mahoney).
// See http://encode.ru/threads/1738-TANGELO-new-compressor-(derived-from-PAQ8-FP8)
type TPAQPredictor struct {
pr int // next predicted value (0-4095)
c0 int32 // bitwise context: last 0-7 bits with a leading 1 (1-255)
c4 int32 // last 4 whole bytes, last is in low 8 bits
c8 int32 // last 8 to 4 whole bytes, last is in low 8 bits
bpos uint // number of bits in c0 (0-7)
pos int32
binCount int32
matchLen int32
matchPos int32
hash int32
statesMask int32
mixersMask int32
hashMask int32
sse0 *LogisticAdaptiveProbMap
sse1 *LogisticAdaptiveProbMap
mixers []TPAQMixer
mixer *TPAQMixer // current mixer
buffer []int8
hashes []int32 // hash table(context, buffer position)
bigStatesMap []uint8 // hash table(context, prediction)
smallStatesMap0 []uint8 // hash table(context, prediction)
smallStatesMap1 []uint8 // hash table(context, prediction)
cp0 *uint8 // context pointers
cp1 *uint8
cp2 *uint8
cp3 *uint8
cp4 *uint8
cp5 *uint8
cp6 *uint8
ctx0 int32 // contexts
ctx1 int32
ctx2 int32
ctx3 int32
ctx4 int32
ctx5 int32
ctx6 int32
extra bool
}
// NewTPAQPredictor creates a new instance of TPAQPredictor using the provided
// map of options to select the sizes of internal structures.
func NewTPAQPredictor(ctx *map[string]interface{}) (*TPAQPredictor, error) {
this := new(TPAQPredictor)
statesSize := 1 << 28
mixersSize := 1 << 12
hashSize := _TPAQ_HASH_SIZE
this.extra = false
extraMem := uint(0)
if ctx != nil {
// If extra mode, add more memory for states table, hash table
// and add second SSE
if val, containsKey := (*ctx)["codec"]; containsKey {
codec := val.(string)
this.extra = codec == "TPAQX"
}
if this.extra == true {
extraMem = 1
}
// Block size requested by the user
// The user can request a big block size to force more states
rbsz := (*ctx)["blockSize"].(uint)
if rbsz >= 64*1024*1024 {
statesSize = 1 << 29
} else if rbsz >= 16*1024*1024 {
statesSize = 1 << 28
} else if rbsz >= 1024*1024 {
statesSize = 1 << 27
} else {
statesSize = 1 << 26
}
// Actual size of the current block
// Too many mixers hurts compression for small blocks.
// Too few mixers hurts compression for big blocks.
absz := (*ctx)["size"].(uint)
if absz >= 32*1024*1024 {
mixersSize = 1 << 17
} else if absz >= 16*1024*1024 {
mixersSize = 1 << 16
} else if absz >= 8*1024*1024 {
mixersSize = 1 << 14
} else if absz >= 4*1024*1024 {
mixersSize = 1 << 12
} else if absz >= 1024*1024 {
mixersSize = 1 << 10
} else {
mixersSize = 1 << 9
}
}
mixersSize <<= extraMem
statesSize <<= extraMem
hashSize <<= (2 * extraMem)
this.mixers = make([]TPAQMixer, mixersSize)
for i := range this.mixers {
this.mixers[i].init()
}
this.mixer = &this.mixers[0]
this.pr = 2048
this.c0 = 1
this.bpos = 8
this.bigStatesMap = make([]uint8, statesSize)
this.smallStatesMap0 = make([]uint8, 1<<16)
this.smallStatesMap1 = make([]uint8, 1<<24)
this.hashes = make([]int32, hashSize)
this.buffer = make([]int8, _TPAQ_BUFFER_SIZE)
this.statesMask = int32(statesSize - 1)
this.mixersMask = int32(mixersSize - 1)
this.hashMask = int32(hashSize - 1)
this.cp0 = &this.smallStatesMap0[0]
this.cp1 = &this.smallStatesMap1[0]
this.cp2 = &this.bigStatesMap[0]
this.cp3 = &this.bigStatesMap[0]
this.cp4 = &this.bigStatesMap[0]
this.cp5 = &this.bigStatesMap[0]
this.cp6 = &this.bigStatesMap[0]
var err error
if this.extra == true {
this.sse0, err = newLogisticAdaptiveProbMap(256, 6)
if err == nil {
this.sse1, err = newLogisticAdaptiveProbMap(65536, 7)
}
} else {
this.sse0, err = newLogisticAdaptiveProbMap(256, 7)
}
return this, err
}
// Update updates the internal probability model based on the observed bit
func (this *TPAQPredictor) Update(bit byte) {
y := int(bit)
this.mixer.update(y)
this.bpos--
this.c0 = (this.c0 << 1) | int32(bit)
if this.c0 > 255 {
this.buffer[this.pos&_TPAQ_MASK_BUFFER] = int8(this.c0)
this.pos++
this.c8 = (this.c8 << 8) | ((this.c4 >> 24) & 0xFF)
this.c4 = (this.c4 << 8) | (this.c0 & 0xFF)
this.hash = (((this.hash * _TPAQ_HASH) << 4) + this.c4) & this.hashMask
this.c0 = 1
this.bpos = 8
this.binCount += ((this.c4 >> 7) & 1)
// Select Neural Net
this.mixer = &this.mixers[this.c4&this.mixersMask]
// Add contexts to NN
this.ctx0 = (this.c4 & 0xFF) << 8
this.ctx1 = (this.c4 & 0xFFFF) << 8
this.ctx2 = createContext(2, this.c4&0x00FFFFFF)
this.ctx3 = createContext(3, this.c4)
if this.binCount < this.pos>>2 {
// Mostly text or mixed
this.ctx4 = createContext(this.ctx1, this.c4^(this.c8&0xFFFF))
this.ctx5 = (this.c8 & _TPAQ_MASK_F0F0F000) | ((this.c4 & _TPAQ_MASK_F0F0F000) >> 4)
if this.extra == true {
var h1, h2 int32
if this.c4&_TPAQ_MASK_80808080 == 0 {
h1 = this.c4 & _TPAQ_MASK_4F4FFFFF
} else {
h1 = this.c4 & _TPAQ_MASK_80808080
}
if this.c8&_TPAQ_MASK_80808080 == 0 {
h2 = this.c8 & _TPAQ_MASK_4F4FFFFF
} else {
h2 = this.c8 & _TPAQ_MASK_80808080
}
this.ctx6 = hashTPAQ(h1<<2, h2>>2)
}
} else {
// Mostly binary
this.ctx4 = createContext(_TPAQ_HASH, this.c4^(this.c4&0x000FFFFF))
this.ctx5 = this.ctx0 | (this.c8 << 16)
if this.extra == true {
this.ctx6 = hashTPAQ(this.c4&_TPAQ_MASK_FFFF0000, this.c8>>16)
}
}
this.findMatch()
// Keep track of current position
this.hashes[this.hash] = this.pos
}
// Get initial predictions
// It has been observed that accessing memory via [ctx ^ c] is significantly faster
// on SandyBridge/Windows and slower on SkyLake/Linux except when [ctx & 255 == 0]
// (with c < 256). Hence, use XOR for _ctx5 which is the only context that fullfills
// the condition.
c := this.c0
table := _TPAQ_STATE_TRANSITIONS[bit]
*this.cp0 = table[*this.cp0]
*this.cp1 = table[*this.cp1]
*this.cp2 = table[*this.cp2]
*this.cp3 = table[*this.cp3]
*this.cp4 = table[*this.cp4]
*this.cp5 = table[*this.cp5]
this.cp0 = &this.smallStatesMap0[this.ctx0+c]
p0 := _TPAQ_STATE_MAP[*this.cp0]
this.cp1 = &this.smallStatesMap1[this.ctx1+c]
p1 := _TPAQ_STATE_MAP[*this.cp1]
this.cp2 = &this.bigStatesMap[(this.ctx2+c)&this.statesMask]
p2 := _TPAQ_STATE_MAP[*this.cp2]
this.cp3 = &this.bigStatesMap[(this.ctx3+c)&this.statesMask]
p3 := _TPAQ_STATE_MAP[*this.cp3]
this.cp4 = &this.bigStatesMap[(this.ctx4+c)&this.statesMask]
p4 := _TPAQ_STATE_MAP[*this.cp4]
this.cp5 = &this.bigStatesMap[(this.ctx5^c)&this.statesMask]
p5 := _TPAQ_STATE_MAP[*this.cp5]
p7 := int32(0)
if this.matchLen != 0 {
p7 = this.getMatchContextPred()
}
var p int
if this.extra == false {
// Mix predictions using NN
p = this.mixer.get(p0, p1, p2, p3, p4, p5, p7, p7)
// SSE (Secondary Symbol Estimation)
if this.binCount < (this.pos >> 3) {
p = this.sse0.get(y, p, int(this.c0))
}
} else {
// One more prediction
*this.cp6 = table[*this.cp6]
this.cp6 = &this.bigStatesMap[(this.ctx6+c)&this.statesMask]
p6 := _TPAQ_STATE_MAP[*this.cp6]
// Mix predictions using NN
p = this.mixer.get(p0, p1, p2, p3, p4, p5, p6, p7)
// SSE (Secondary Symbol Estimation)
if this.binCount < (this.pos >> 3) {
p = this.sse1.get(y, p, int(this.ctx0+c))
} else {
if this.binCount >= (this.pos >> 2) {
p = (3*this.sse0.get(y, p, int(this.c0)) + p) >> 2
}
p = (3*this.sse1.get(y, p, int(this.ctx0+c)) + p) >> 2
}
}
this.pr = p + int(uint32(p-2048)>>31)
}
// Get returns the value representing the probability of the next bit being
// 1 (in the [0..4095] range).
func (this *TPAQPredictor) Get() int {
return this.pr
}
func (this *TPAQPredictor) findMatch() {
// Update ongoing sequence match or detect match in the buffer (LZ like)
if this.matchLen > 0 {
if this.matchLen < _TPAQ_MAX_LENGTH {
this.matchLen++
}
this.matchPos++
} else {
// Retrieve match position
this.matchPos = this.hashes[this.hash]
// Detect match
if this.matchPos != 0 && this.pos-this.matchPos <= _TPAQ_MASK_BUFFER {
r := this.matchLen + 2
s := this.pos - r
t := this.matchPos - r
for r <= _TPAQ_MAX_LENGTH {
if this.buffer[s&_TPAQ_MASK_BUFFER] != this.buffer[t&_TPAQ_MASK_BUFFER] {
break
}
if this.buffer[(s-1)&_TPAQ_MASK_BUFFER] != this.buffer[(t-1)&_TPAQ_MASK_BUFFER] {
break
}
r += 2
s -= 2
t -= 2
}
this.matchLen = r - 2
}
}
}
// Get a squashed prediction (in [-2047..2048]) from the match model
func (this *TPAQPredictor) getMatchContextPred() int32 {
if this.c0 == ((int32(this.buffer[this.matchPos&_TPAQ_MASK_BUFFER])&0xFF)|256)>>this.bpos {
var p int32
if this.matchLen <= 24 {
p = this.matchLen
} else {
p = (24 + ((this.matchLen - 24) >> 3))
}
if ((this.buffer[this.matchPos&_TPAQ_MASK_BUFFER] >> (this.bpos - 1)) & 1) == 0 {
return -p << 6
}
return p << 6
}
this.matchLen = 0
return 0
}
func createContext(ctxID, cx int32) int32 {
c := uint32(cx*987654323 + ctxID)
c = bits.RotateLeft32(c, 16)
return int32(c*123456791) + ctxID
}
// TPAQMixer a mixer that combines models using neural networks with 8 inputs.
type TPAQMixer struct {
pr int // squashed prediction
skew int32
w0, w1, w2, w3, w4, w5, w6, w7 int32
p0, p1, p2, p3, p4, p5, p6, p7 int32
learnRate int32
}
func (this *TPAQMixer) init() {
this.pr = 2048
this.skew = 0
this.w0 = 32768
this.w1 = 32768
this.w2 = 32768
this.w3 = 32768
this.w4 = 32768
this.w5 = 32768
this.w6 = 32768
this.w7 = 32768
this.learnRate = _TPAQ_BEGIN_LEARN_RATE
}
// Adjust weights to minimize coding cost of last prediction
func (this *TPAQMixer) update(bit int) {
err := (int32((bit<<12)-this.pr) * this.learnRate) >> 10
if err == 0 {
return
}
// Quickly decaying learn rate
this.learnRate += ((_TPAQ_END_LEARN_RATE - this.learnRate) >> 31)
this.skew += err
// Train Neural Network: update weights
this.w0 += ((this.p0*err + 0) >> 12)
this.w1 += ((this.p1*err + 0) >> 12)
this.w2 += ((this.p2*err + 0) >> 12)
this.w3 += ((this.p3*err + 0) >> 12)
this.w4 += ((this.p4*err + 0) >> 12)
this.w5 += ((this.p5*err + 0) >> 12)
this.w6 += ((this.p6*err + 0) >> 12)
this.w7 += ((this.p7*err + 0) >> 12)
}
// Returns a prediction by mixing the predictions provided as input
func (this *TPAQMixer) get(p0, p1, p2, p3, p4, p5, p6, p7 int32) int {
this.p0 = p0
this.p1 = p1
this.p2 = p2
this.p3 = p3
this.p4 = p4
this.p5 = p5
this.p6 = p6
this.p7 = p7
// Neural Network dot product (sum weights*inputs)
this.pr = kanzi.Squash(int((this.w0*p0 + this.w1*p1 + this.w2*p2 + this.w3*p3 +
this.w4*p4 + this.w5*p5 + this.w6*p6 + this.w7*p7 +
this.skew + 65536) >> 17))
return this.pr
}