I think you're mistaken about how similar ? and ?. are.
They share a structure at a high level, but a couple of years ago I made improvements to the algorithms used in ? . We decided at that time that these improvements would not be put into ?. to keep compatibility to old test streams that depend on ?.'s producing its fixed sequence.
Also, I think that ?. just uses the old Lehmer linear-congruential generator rather than the faster better ones in ? .
You should not make any changes that will alter the sequence generated by ?. . Improvements to ? are welcome.
Henry Rich On 11/22/2022 6:31 PM, Raul Miller wrote:
Currently, in my work-in-progress branch, integrating libgmp support into the j engine, in vrand.c the implementation for generating random XNUM values needs a bit of work. (Today I addressed an unhandled issue I had left for myself earlier, where ?.2x (or any other positive extended integer) would segfault. That was a necessary effort, but it didn't go far enough.) There's at least two issues I'd like to call out: (1) Code duplication between ?. and ? (2) jtrollxnum vs jtxrand Taking these in order: (1) Currently, for every routine supporting ? there's a nearly identical clone of it supporting ?. Conceptually, if our integrated rank support was structured suitably (an issue I am not currently in a position to judge), we could discard the ?. specific routines, replacing them with one or more routines which seed the random number generator appropriately before invoking the random number generating process, then restoring the state of the random number generator afterwards. (2) Currently, the implementation of jtxranddot is probably what I should be using for jtxrand. Currently, the implementation of jtxroll ignores the implementation of jtxrand and instead calls a libgmp specific routine. This is an issue with several faces, but one of them is that ?. currently does support the various J RNG algorithms, while ? only supports one algorithm. I need to also review the information available to me -- it might be that the state space for the libgmp random number generator is larger than that used in the J implementation, or it might be that the size of the state space is constrained by the algorithm. If any of these issues fall comfortably inside where anyone wants to spend time, I'd welcome any assistance offered. (Otherwise, I'll continue to slowly plow through cataloging and working through these issues.) Thanks,
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