Skipping duplicat moves

[Michael Sherwin]

To get deeper faster there are really only two considerations. The first is what can be done to minimize the number of qsearch calls and two is having the fastest possible qsearch for your needs. Everything else has very little impact. Searching duplicate moves is bad because it increases noticeably the number of qsearch calls. Better move ordering reduces dramatically the number of qsearch calls. Any reasonable amount of extra work done to reduce the number of qsearch calls will have very little impact on nps.