I hope this isn't too much of an arbitrary question, but I have been looking through the source codes of Faile and TSCP and I have been playing them against each other. As far as I can see the engines have a lot in common, yet Faile searches ~1.3 million nodes per second while TSCP searches only 300k nodes per second.
The source code for faile can be found here: http://faile.sourceforge.net/download.php. TSCP source code can be found here: http://www.tckerrigan.com/Chess/TSCP.
After looking through them I see some similarities: both use an array board representation (although Faile uses a 144 size board), both use a alpha beta search with some sort of transposition table, both have very similar evaluate functions. The main difference I can find is that Faile uses a redundant representation of the board by also having arrays of the piece locations. This means that when the moves are generated (by very similar functions for both programs), Faile has to for loop through fewer bad pieces, while maintaining this array costs considerably fewer resources.
My question is: why is there a 4x difference in the speed of these two programs? Also, why does Faile consistently beat TSCP (I estimate about a ~200 ELO difference just by watching their moves)? For the latter, it seems to be because Faile is searching several plies deeper.
TSCP has not hash tables (-75 ELO). TSCP has not Killers moves for ordering (-50 ELO). TSCP has not null move (-100 ELO). TSCP has a bad attack function design (-25 ELO).
In these 4 things you have about a difference of 250 points ELO. This will increase the number of nodes per second but you can not compare nodes per second on different engines as programmers can use a different interpretation of what is a node.