Stop the depth decrease at half the root depth.

lucabrivio · lucabrivio · commit ac9ab10ea1f1 · 2018-09-17T21:56:30.000+02:00
Bench: 3328997
diff --git a/src/search.cpp b/src/search.cpp
@@ -398,7 +398,7 @@ void Thread::search() {
           int failedHighCnt = 0;
           while (true)
           {
-              adjustedDepth = std::max(ONE_PLY, rootDepth - failedHighCnt * ONE_PLY);
+              adjustedDepth = std::max(ONE_PLY, std::max(rootDepth / 2, rootDepth - failedHighCnt * ONE_PLY));
               bestValue = ::search<PV>(rootPos, ss, alpha, beta, adjustedDepth, false);
 
               // Bring the best move to the front. It is critical that sorting

Original file line number	Diff line number	Diff line change
`@@ -398,7 +398,7 @@ void Thread::search() {`
`398`	`398`	`int failedHighCnt = 0;`
`399`	`399`	`while (true)`
`400`	`400`	`{`
`401`		`- adjustedDepth = std::max(ONE_PLY, rootDepth - failedHighCnt * ONE_PLY);`
	`401`	`+ adjustedDepth = std::max(ONE_PLY, std::max(rootDepth / 2, rootDepth - failedHighCnt * ONE_PLY));`
`402`	`402`	`bestValue = ::search<PV>(rootPos, ss, alpha, beta, adjustedDepth, false);`
`403`	`403`
`404`	`404`	`// Bring the best move to the front. It is critical that sorting`