tsai
/
ImageSharp
mirror of https://github.com/SixLabors/ImageSharp
1
0
Fork 0
Code Issues Projects Releases Wiki Activity
Browse Source

Add SSE version of CombinedShannonEntropy

pull/1848/head
Brian Popow 4 years ago
parent
2c5c9f1b63
commit
bab85d4372
1 changed files with 137 additions and 17 deletions
Whitespace
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
Split View
Diff Options
Show Stats Download Patch File Download Diff File
  1. 154
      src/ImageSharp/Formats/Webp/Lossless/LosslessUtils.cs

154
src/ImageSharp/Formats/Webp/Lossless/LosslessUtils.cs
View File

@ -759,28 +759,147 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless
/// <returns>Shanon entropy.</returns>
public static float CombinedShannonEntropy(Span<int> x, Span<int> y)
{
double retVal = 0.0d;
uint sumX = 0, sumXY = 0;
for (int i = 0; i < 256; i++)
{
uint xi = (uint)x[i];
if (xi != 0)
#if SUPPORTS_RUNTIME_INTRINSICS
if (Sse41.IsSupported)
{
double retVal = 0.0d;
Span<int> tmp = stackalloc int[4];
ref int xRef = ref MemoryMarshal.GetReference(x);
ref int yRef = ref MemoryMarshal.GetReference(y);
Vector128<int> sumXY128 = Vector128<int>.Zero;
Vector128<int> sumX128 = Vector128<int>.Zero;
ref int tmpRef = ref MemoryMarshal.GetReference(tmp);
for (int i = 0; i < 256; i += 4)
{
uint xy = xi + (uint)y[i];
sumX += xi;
retVal -= FastSLog2(xi);
sumXY += xy;
retVal -= FastSLog2(xy);
Vector128<int> xVec = Unsafe.As<int, Vector128<int>>(ref Unsafe.Add(ref xRef, i));
Vector128<int> yVec = Unsafe.As<int, Vector128<int>>(ref Unsafe.Add(ref yRef, i));
// Check if any X is non-zero: this actually provides a speedup as X is usually sparse.
if (Sse2.MoveMask(Sse2.CompareEqual(xVec, Vector128<int>.Zero).AsByte()) != 0xFFFF)
{
Vector128<int> xy128 = Sse2.Add(xVec, yVec);
sumXY128 = Sse2.Add(sumXY128, xy128);
sumX128 = Sse2.Add(sumX128, xVec);
// Analyze the different X + Y.
Unsafe.As<int, Vector128<int>>(ref tmpRef) = xy128;
if (tmp[0] != 0)
{
retVal -= FastSLog2((uint)tmp[0]);
if (x[i + 0] != 0)
{
retVal -= FastSLog2((uint)x[i + 0]);
}
}
if (tmp[1] != 0)
{
retVal -= FastSLog2((uint)tmp[1]);
if (x[i + 1] != 0)
{
retVal -= FastSLog2((uint)x[i + 1]);
}
}
if (tmp[2] != 0)
{
retVal -= FastSLog2((uint)tmp[2]);
if (x[i + 2] != 0)
{
retVal -= FastSLog2((uint)x[i + 2]);
}
}
if (tmp[3] != 0)
{
retVal -= FastSLog2((uint)tmp[3]);
if (x[i + 3] != 0)
{
retVal -= FastSLog2((uint)x[i + 3]);
}
}
}
else
{
// X is fully 0, so only deal with Y.
sumXY128 = Sse2.Add(sumXY128, yVec);
if (y[i] != 0)
{
retVal -= FastSLog2((uint)y[i]);
}
if (y[i + 1] != 0)
{
retVal -= FastSLog2((uint)y[i + 1]);
}
if (y[i + 2] != 0)
{
retVal -= FastSLog2((uint)y[i + 2]);
}
if (y[i + 3] != 0)
{
retVal -= FastSLog2((uint)y[i + 3]);
}
}
}
else if (y[i] != 0)
// Sum up sumX_128 to get sumX and sum up sumXY_128 to get sumXY.
// note: not using here Numerics.ReduceSum, because grouping the same methods together should be slightly faster.
Vector128<int> haddSumX = Ssse3.HorizontalAdd(sumX128, sumX128);
Vector128<int> haddSumXY = Ssse3.HorizontalAdd(sumXY128, sumXY128);
Vector128<int> swappedSumX = Sse2.Shuffle(haddSumX, 0x1);
Vector128<int> swappedSumXY = Sse2.Shuffle(haddSumXY, 0x1);
Vector128<int> tmpSumX = Sse2.Add(haddSumX, swappedSumX);
Vector128<int> tmpSumXY = Sse2.Add(haddSumXY, swappedSumXY);
int sumX = Sse2.ConvertToInt32(tmpSumX);
int sumXY = Sse2.ConvertToInt32(tmpSumXY);
retVal += FastSLog2((uint)sumX) + FastSLog2((uint)sumXY);
return (float)retVal;
}
else
#endif
{
double retVal = 0.0d;
uint sumX = 0, sumXY = 0;
for (int i = 0; i < 256; i++)
{
sumXY += (uint)y[i];
retVal -= FastSLog2((uint)y[i]);
uint xi = (uint)x[i];
if (xi != 0)
{
uint xy = xi + (uint)y[i];
sumX += xi;
retVal -= FastSLog2(xi);
sumXY += xy;
retVal -= FastSLog2(xy);
}
else if (y[i] != 0)
{
sumXY += (uint)y[i];
retVal -= FastSLog2((uint)y[i]);
}
}
retVal += FastSLog2(sumX) + FastSLog2(sumXY);
return (float)retVal;
}
}
retVal += FastSLog2(sumX) + FastSLog2(sumXY);
return (float)retVal;
[MethodImpl(InliningOptions.ShortMethod)]
private static void AnalyzeXy(Span<int> tmp, Span<int> x, int i, int pos, ref double retVal)
{
if (tmp[pos] != 0)
{
retVal -= FastSLog2((uint)tmp[pos]);
if (x[i + pos] != 0)
{
retVal -= FastSLog2((uint)x[i + pos]);
}
}
}
[MethodImpl(InliningOptions.ShortMethod)]
@ -836,6 +955,7 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless
private static float FastSLog2Slow(uint v)
{
DebugGuard.MustBeGreaterThanOrEqualTo<uint>(v, LogLookupIdxMax, nameof(v));
if (v < ApproxLogWithCorrectionMax)
{
int logCnt = 0;
@ -865,7 +985,7 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless
private static float FastLog2Slow(uint v)
{
Guard.MustBeGreaterThanOrEqualTo(v, LogLookupIdxMax, nameof(v));
DebugGuard.MustBeGreaterThanOrEqualTo<uint>(v, LogLookupIdxMax, nameof(v));
if (v < ApproxLogWithCorrectionMax)
{

Write Preview
Loading…
Cancel
Save