public UnsafeMatrix <T> Multiply <T>(UnsafeMatrix <T> a, UnsafeMatrix <T> b, int blockSize)
{
if (!a.CanMultiplyWith(b))
{
throw new ArgumentException();
}
int ar = a.Rows;
int ac = a.Columns;
int br = b.Rows;
int bc = b.Columns;
if (ar % blockSize != 0 || ac % blockSize != 0 ||
br % blockSize != 0 || bc % blockSize != 0)
{
throw new IndexOutOfRangeException();
}
UnsafeMatrix <T> result = new UnsafeMatrix <T>(new T[ar, bc]);
int processCount = (ar * bc) / (blockSize * blockSize);
int blocksPerProcess = ac / blockSize;
int multiplicationsPerBlock = bc / blockSize;
Thread[] threads = new Thread[processCount];
for (int i = 0; i < processCount; i++)
{
UnsafeMatrix <T>[] blocksA = new UnsafeMatrix <T> [blocksPerProcess];
UnsafeMatrix <T>[] blocksB = new UnsafeMatrix <T> [blocksPerProcess];
int row = (i / multiplicationsPerBlock) * blockSize;
int col = (i % multiplicationsPerBlock) * blockSize;
for (int j = 0; j < blocksPerProcess; j++)
{
blocksA[j] = a.GetBlock(row, j * blockSize, blockSize, blockSize);
blocksB[j] = b.GetBlock(j * blockSize, col, blockSize, blockSize);
}
threads[i] = new Thread(() => Multiply(result, blocksA, blocksB, row, col, blockSize));
threads[i].Start();
}
foreach (Thread t in threads)
{
t.Join();
}
return(result);
}
private static void Multiply <T>(
UnsafeMatrix <T> result,
UnsafeMatrix <T>[] blocksA,
UnsafeMatrix <T>[] blocksB,
int row,
int col,
int size)
{
Debug.Assert(blocksA.Length == blocksB.Length);
UnsafeMatrix <T> sumOfProducts = null;
for (int k = 0; k < blocksA.Length; k++)
{
UnsafeMatrix <T> toAdd = blocksA[k].Mul(blocksB[k]);
sumOfProducts = sumOfProducts == null ? toAdd : sumOfProducts + toAdd;
}
result.SetBlock(row, col, sumOfProducts);
}
