Oh, I don't know that there's a way to do that. The G++ implementation uses free memory if available for linear merge, else it falls back to n log n merge. I

Oh, I don't know that there's a way to do that. The G++ implementation uses free memory if available for linear merge, else it falls back to n log n merge. I don't think this affects the performance of insert though (which is already log n due to the necessary lookup).