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Annotation of elwix/tools/oldlzma/SRC/7zip/Compress/RangeCoder/RangeCoderBit.cpp, revision 1.1.1.1

1.1       misho       1: // Compress/RangeCoder/RangeCoderBit.cpp
                      2: 
                      3: #include "StdAfx.h"
                      4: 
                      5: #include "RangeCoderBit.h"
                      6: 
                      7: namespace NCompress {
                      8: namespace NRangeCoder {
                      9: 
                     10: UInt32 CPriceTables::ProbPrices[kBitModelTotal >> kNumMoveReducingBits];
                     11: static CPriceTables g_PriceTables;
                     12: 
                     13: CPriceTables::CPriceTables() { Init(); }
                     14: 
                     15: void CPriceTables::Init()
                     16: {
                     17:   const int kNumBits = (kNumBitModelTotalBits - kNumMoveReducingBits);
                     18:   for(int i = kNumBits - 1; i >= 0; i--)
                     19:   {
                     20:     UInt32 start = 1 << (kNumBits - i - 1);
                     21:     UInt32 end = 1 << (kNumBits - i);
                     22:     for (UInt32 j = start; j < end; j++)
                     23:       ProbPrices[j] = (i << kNumBitPriceShiftBits) + 
                     24:           (((end - j) << kNumBitPriceShiftBits) >> (kNumBits - i - 1));
                     25:   }
                     26: 
                     27:   /*
                     28:   // simplest: bad solution
                     29:   for(UInt32 i = 1; i < (kBitModelTotal >> kNumMoveReducingBits) - 1; i++)
                     30:     ProbPrices[i] = kBitPrice;
                     31:   */
                     32:   
                     33:   /*
                     34:   const double kDummyMultMid = (1.0 / kBitPrice) / 2;
                     35:   const double kDummyMultMid = 0;
                     36:   // float solution
                     37:   double ln2 = log(double(2));
                     38:   double lnAll = log(double(kBitModelTotal >> kNumMoveReducingBits));
                     39:   for(UInt32 i = 1; i < (kBitModelTotal >> kNumMoveReducingBits) - 1; i++)
                     40:     ProbPrices[i] = UInt32((fabs(lnAll - log(double(i))) / ln2 + kDummyMultMid) * kBitPrice);
                     41:   */
                     42:   
                     43:   /*
                     44:   // experimental, slow, solution:
                     45:   for(UInt32 i = 1; i < (kBitModelTotal >> kNumMoveReducingBits) - 1; i++)
                     46:   {
                     47:     const int kCyclesBits = 5;
                     48:     const UInt32 kCycles = (1 << kCyclesBits);
                     49: 
                     50:     UInt32 range = UInt32(-1);
                     51:     UInt32 bitCount = 0;
                     52:     for (UInt32 j = 0; j < kCycles; j++)
                     53:     {
                     54:       range >>= (kNumBitModelTotalBits - kNumMoveReducingBits);
                     55:       range *= i;
                     56:       while(range < (1 << 31))
                     57:       {
                     58:         range <<= 1;
                     59:         bitCount++;
                     60:       }
                     61:     }
                     62:     bitCount <<= kNumBitPriceShiftBits;
                     63:     range -= (1 << 31);
                     64:     for (int k = kNumBitPriceShiftBits - 1; k >= 0; k--)
                     65:     {
                     66:       range <<= 1;
                     67:       if (range > (1 << 31))
                     68:       {
                     69:         bitCount += (1 << k);
                     70:         range -= (1 << 31);
                     71:       }
                     72:     }
                     73:     ProbPrices[i] = (bitCount 
                     74:       // + (1 << (kCyclesBits - 1))
                     75:       ) >> kCyclesBits;
                     76:   }
                     77:   */
                     78: }
                     79: 
                     80: }}