public static List <int[]> GetNearestNeighbours(List <double[]> samples, NNAlgorithm nnMethod, int numThreads = 1)
{
int numDim = samples[0].Length;
int numSamples = samples.Count;
if (numThreads == 1 || numSamples < 500)
{
return(nnMethod.GetNearestNeighbours(samples, 0, numSamples));
}
else
{
int[,] indexes = GetIndexes(samples.Count, numThreads);
List <int[]> results = RunThreads(samples, nnMethod, indexes, numThreads);
results.Sort(new IntComp()); // sort to make sure are in the order of the index and not the order they were threaded
return(results);
}
}
private static List <int[]> RunThreads(List <double[]> samples, NNAlgorithm algorithm, int[,] indexes, int numThreads)
{
Task <List <int[]> >[] taskArray = new Task <List <int[]> > [numThreads];
// start theads
for (int iter = 0; iter < numThreads; iter++)
{
int tstart_idx = indexes[iter, 0]; // must copy local here see:
int tend_idx = indexes[iter, 1]; // must copy local here see:
taskArray[iter] = Task <List <int[]> > .Factory.StartNew(() => { return(algorithm.GetNearestNeighbours(samples, tstart_idx, tend_idx)); });
}
// get results
List <int[]> results = new List <int[]>();
for (int iter = 0; iter < numThreads; iter++)
{
results.AddRange(taskArray[iter].Result); // .Result will block until thread is finished.
}
return(results);
}
