public static void AlltoallSubarrays <T>(ICommunicator comm, IReadOnlyList <T> inputArray, ICollection <int>[] indicesToSend, IList <T> outputArray, ICollection <int>[] indicesToReceive)
{
var sendCounts = indicesToSend.Select(indices => indices.Count).ToArray();
var sendTotalCount = sendCounts.Sum();
T[] subarrayToSend = new T[sendTotalCount];
int position = 0;
for (int recipient = 0; recipient < indicesToSend.Length; recipient++)
{
foreach (int index in indicesToSend[recipient])
{
//if (comm.Rank == 0 && recipient == 1)
// Trace.WriteLine($"sending {inputArray[index]}");
subarrayToSend[position++] = inputArray[index];
}
}
var recvCounts = indicesToReceive.Select(indices => indices.Count).ToArray();
var recvTotalCount = recvCounts.Sum();
AlltoallSubarraysItemsTransmitted += sendTotalCount + recvTotalCount;
T[] subarrayReceived = comm.AlltoallFlattened(subarrayToSend, sendCounts, recvCounts);
int recvPosition = 0;
for (int source = 0; source < comm.Size; source++)
{
var indicesOfSubarray = indicesToReceive[source];
foreach (int index in indicesOfSubarray)
{
outputArray[index] = subarrayReceived[recvPosition++];
//Trace.WriteLine($"process {comm.Rank} from {source} received {outputArray[index]} for local index {index} recvPosition = {recvPosition}");
}
}
}
