futility pruning - razoring

[Don]

At the time of that discussion, 99% of the chess program authors extended to get out of check, rather than to extend when giving check. I think I was the first to extend when giving check, for that very reason. They sound the same, but they are not quite the same.

I have never extended the out of check moves. I have not been programming chess for as long as you have, but I think my first program was written in 1985.

That was way back in the last century.

- Don

[bob]

At the time of that discussion, 99% of the chess program authors extended to get out of check, rather than to extend when giving check. I think I was the first to extend when giving check, for that very reason. They sound the same, but they are not quite the same.

I have never extended the out of check moves. I have not been programming chess for as long as you have, but I think my first program was written in 1985.

That was way back in the last century.

- Don

In the day, Cray Blitz, Belle, deep thought, chaos, laches, nuchess/chess 4.x, all extended when getting out of check. The only real effect of this is that you never get to the q-search when in check. But in those days, that did not matter, as at least in our case, the q-search was handled differently and we actually escaped check in the first 4 plies of the q-search anyway. It was a wash and probably more efficient to extend that way since the tree was a bit smaller.