Among the 9 endings that are directly influenced by the 50-move rule (knnkp, kqpkq, kbbkn, kbnkn, krbkr, kqrkq, krpkq, kbbkq, knnkq), the first 6 ones are already generated and the results are the following :
knnkp : The 50-move rule begins to strike at depth=52 and beyond this depth it has a considerable effect on the play for almost any position. As a consequence the maximal DTM50 positions are totally different from the maximal DTM positions. At movecount = 0 the longest DTM50 win is 112 moves, one of the maximal positions is Ka3 Na4 Nf2 / Ka6 Ph7 (wtm – 223 plies). If the movecounter in the initial position can be > 0, the longest DTM50 win tops out at 128 moves, one example is Kc3 Nb1 Nf6 / Ka3 Pa5 mc=4 or 5 plies (btm – 256 plies)
kqpkq : The 50-move rule effect begins at depth=59. Beyond this depth, a lot of wins are delayed by a few moves owing to the necessity of the winning side to push his pawn every 50 moves. The longest win is a mate in 137 (I’ll post a position and its winning line soon), so the DTM record for 5-men (127 moves in kppkp) is beaten
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kbbkn : The 50-move rule begins its effects at depth=56 and the maximal DTM50 value is 66. It seems that between these values DTM50 play can differ from DTZ50 or DTM play before reaching the Kling & Horwitz pseudo-fortress, but I haven’t checked this yet.
kbnkn : The 50-move rule begins its effects at depth=65 where it influences a very small fraction of the positions (<1%). This situation (tiny percentage of positions affected) remains up to depth=80 where there is a brutal cutoff, 80 being the maximal DTM50 value and all positions with DTM>=81 being 50 move rule draws.
krbkr : This ending has the special property of having all its deepest positions merging into a single variant that is both DTM and DTZ50 optimal. The result is that the 50-move rule effect is a simple cutoff at DTM=56 : All positions with DTM<=56 are winning under 50-move rule with DTM50=DTM, and all positions with DTM>=57 are 50-move rule draws.
kqrkq : Positions with DTM<=54 are unaffected by the 50-move rule. At depth >=55, some positions remain winning with DTM50=DTM, some become 50-move rule draws and some are still winnable but with DTM50>DTM because Black is able to engage a variant in which he is able to force an exchange of queens in the last phase of the game instead of being forced to give up queen for rook (or being mated). One of the maximal positions is Ka1 Qa8 Ra2 / Kg7 Qa4 (btm), with DTM=56 and DTM50=61.