}
-/// TranspositionTable::clear() overwrites the entire transposition table
-/// with zeros. It is called whenever the table is resized, or when the
-/// user asks the program to clear the table (from the UCI interface).
-/// It starts as many threads as allowed by the Threads option.
+/// TranspositionTable::clear() initializes the entire transposition table to zero,
+// in a multi-threaded way.
void TranspositionTable::clear() {
- const size_t stride = clusterCount / Options["Threads"];
std::vector<std::thread> threads;
+
for (size_t idx = 0; idx < Options["Threads"]; idx++)
{
- const size_t start = stride * idx,
- len = idx != Options["Threads"] - 1 ?
- stride :
- clusterCount - start;
- threads.push_back(std::thread([this, idx, start, len]() {
+ threads.push_back(std::thread([this, idx]() {
+
+ // Thread binding gives faster search on systems with a first-touch policy
if (Options["Threads"] >= 8)
WinProcGroup::bindThisThread(idx);
+
+ // Each thread will zero its part of the hash table
+ const size_t stride = clusterCount / Options["Threads"],
+ start = stride * idx,
+ len = idx != Options["Threads"] - 1 ?
+ stride : clusterCount - start;
+
std::memset(&table[start], 0, len * sizeof(Cluster));
}));
}