public (I3DTensor Result, IReadOnlyList <(object X, object Y)> Index) MaxPool(
int filterWidth,
int filterHeight,
int stride,
bool calculateIndex)
{
var newColumns = (ColumnCount - filterWidth) / stride + 1;
var newRows = (RowCount - filterHeight) / stride + 1;
var matrixList = new List <CpuMatrix>();
var indexList = calculateIndex ? new List <(object X, object Y)>() : null;
var posList = ConvolutionHelper.Default(ColumnCount, RowCount, filterWidth, filterHeight, stride);
for (var k = 0; k < Depth; k++)
{
var matrix = _data[k];
var xIndex = new int[newColumns * newRows];
var yIndex = new int[newColumns * newRows];
var layer = new CpuMatrix(DenseMatrix.Create(newRows, newColumns, 0f));
foreach (var item in posList)
{
var first = item.First();
var targetX = first.X / stride;
var targetY = first.Y / stride;
var maxVal = float.MinValue;
var bestX = -1;
var bestY = -1;
foreach (var pos in item)
{
var val = matrix[pos.Y, pos.X];
if (val > maxVal || bestX == -1)
{
bestX = pos.X;
bestY = pos.Y;
maxVal = val;
}
}
var index = targetX * newRows + targetY;
xIndex[index] = bestX;
yIndex[index] = bestY;
layer[targetY, targetX] = maxVal;
}
matrixList.Add(layer);
indexList?.Add((xIndex, yIndex));
}
return(new Cpu3DTensor(matrixList), indexList);
}
public IMatrix Im2Col(int filterWidth, int filterHeight, int stride)
{
var rowList = new List <float[]>();
var convolutions = ConvolutionHelper.Default(ColumnCount, RowCount, filterWidth, filterHeight, stride);
foreach (var filter in convolutions)
{
var row = new float[filter.Length * Depth];
int index = 0;
for (var k = 0; k < Depth; k++)
{
foreach (var item in filter)
{
row[index++] = this[item.Y, item.X, k];
}
}
rowList.Add(row);
}
var firstRow = rowList.First();
return(new CpuMatrix(DenseMatrix.Create(rowList.Count, firstRow.Length, (i, j) => rowList[i][j])));
}