/// <summary>Sorts an array of unsigned integers in parallel.</summary>
public void Sort(int maxShiftWidth = 32)
{
Profiler.BeginSample("RadixSort");
ComputeShaderUtil.ZeroOut(ref cb_sortTemp, _dataSize);
ComputeShaderUtil.ZeroOut(ref cb_indexTemp, _dataSize);
ComputeShaderUtil.ZeroOut(ref cb_prefixSums, _dataSize);
ComputeShaderUtil.ZeroOut(ref cb_blockSums, _blockSumsSize);
ComputeShaderUtil.ZeroOut(ref cb_scanBlockSums, _blockSumsSize);
// for every 2 bits from LSB to MSB:
// block-wise radix sort (write blocks back to global memory)
for (int shiftWidth = 0; shiftWidth < maxShiftWidth; shiftWidth += 2)
{
cs_radixSort.SetInt(PropertyID.shiftWidth, shiftWidth);
cs_radixSort.Dispatch(kn_radixSortLocal, _sortGridSize, 1, 1);
// scan global block sum array
ComputeShaderUtil.ZeroOut(ref cb_scanBlockSums, _blockSumsSize);
_blellochSumScan.Scan(ref cb_blockSums, ref cb_scanBlockSums, _blockSumsSize);
// scatter/shuffle block-wise sorted array to final positions
cs_radixSort.Dispatch(kn_globalShuffle, _sortGridSize, 1, 1);
}
Profiler.EndSample();
}
public void Scan(
ref ComputeBuffer cb_in, ref ComputeBuffer cb_out,
int dataSize, int recurseNum = 0
)
{
Profiler.BeginSample("BlellochSumScan");
int blellochGridSize = _gridSizes[recurseNum];
ComputeBuffer cb_sumScanBlockSum = cb_sumScanBlockSums[recurseNum];
ComputeShaderUtil.ZeroOut(ref cb_sumScanBlockSum, blellochGridSize);
// sum scan data allocated to each block
cs_blellochSumScan.SetInt(PropertyID.len, dataSize);
cs_blellochSumScan.SetBuffer(kn_preSumScan, BufferID.cb_out, cb_out);
cs_blellochSumScan.SetBuffer(kn_preSumScan, BufferID.cb_in, cb_in);
cs_blellochSumScan.SetBuffer(kn_preSumScan, BufferID.cb_blockSums, cb_sumScanBlockSum);
cs_blellochSumScan.Dispatch(kn_preSumScan, blellochGridSize, 1, 1);
// sum scan total sums produced by each block
// use basic implementation if number of total sums is <= 2 * Graphics.M_BLOCK_SZ
// (this requires only one block to do the scan)
if (blellochGridSize <= Graphics.S_BLOCK_SZ)
{
ComputeShaderUtil.ZeroOut(ref cb_dummyGrpSums, 1);
ComputeBuffer cb_preSumScanTemp = cb_preSumScanTemps[recurseNum];
ComputeShaderUtil.CopyBuffer(ref cb_sumScanBlockSum, ref cb_preSumScanTemp, blellochGridSize);
cs_blellochSumScan.SetInt(PropertyID.len, blellochGridSize);
cs_blellochSumScan.SetBuffer(kn_preSumScan, BufferID.cb_out, cb_sumScanBlockSum);
cs_blellochSumScan.SetBuffer(kn_preSumScan, BufferID.cb_in, cb_preSumScanTemp);
cs_blellochSumScan.SetBuffer(kn_preSumScan, BufferID.cb_blockSums, cb_dummyGrpSums);
cs_blellochSumScan.Dispatch(kn_preSumScan, 1, 1, 1);
}
else // else, recurse on this same function as you'll need the full-blown scan for the block sums
{
ComputeBuffer cb_inBlockSum = cb_inBlockSums[recurseNum];
ComputeShaderUtil.CopyBuffer(ref cb_sumScanBlockSum, ref cb_inBlockSum, blellochGridSize);
Scan(ref cb_inBlockSum, ref cb_sumScanBlockSum, blellochGridSize, recurseNum + 1);
}
ComputeBuffer cb_addBlockSumsTemp = cb_addBlockSumsTemps[recurseNum];
ComputeShaderUtil.CopyBuffer(ref cb_out, ref cb_addBlockSumsTemp, dataSize);
// add each block's total sum to its scan output in order to get the final, global scanned array
cs_blellochSumScan.SetInt(PropertyID.len, dataSize);
cs_blellochSumScan.SetBuffer(kn_addBlockSums, BufferID.cb_out, cb_out);
cs_blellochSumScan.SetBuffer(kn_addBlockSums, BufferID.cb_in, cb_addBlockSumsTemp);
cs_blellochSumScan.SetBuffer(kn_addBlockSums, BufferID.cb_blockSums, cb_sumScanBlockSum);
cs_blellochSumScan.Dispatch(kn_addBlockSums, blellochGridSize, 1, 1);
Profiler.EndSample();
}
public void BlellochSumScanTest()
{
uint[] array = new uint[ARRAY_COUNT];
uint[] scannedArray = new uint[ARRAY_COUNT];
for (int i = 0; i < ARRAY_COUNT; i++)
{
array[i] = GenerateRandomUInt();
}
ComputeBuffer cb_in = new ComputeBuffer(ARRAY_COUNT, StrideSize.s_uint);
ComputeBuffer cb_out = new ComputeBuffer(ARRAY_COUNT, StrideSize.s_uint);
ComputeShaderUtil.InitKernels();
BlellochSumScan.InitKernels();
cb_in.SetData(array);
ComputeShaderUtil.ZeroOut(ref cb_out, ARRAY_COUNT);
BlellochSumScan blellochSumScan = new BlellochSumScan(ARRAY_COUNT);
blellochSumScan.Scan(ref cb_in, ref cb_out, ARRAY_COUNT);
cb_out.GetData(scannedArray);
// using serial exclusive sum scan method to make sure that the parallel method works
uint sum = 0;
for (int i = 0; i < ARRAY_COUNT; i++)
{
Assert.AreEqual(sum, scannedArray[i]);
sum += array[i];
}
cb_in.Dispose();
cb_out.Dispose();
blellochSumScan.Dispose();
}