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-   -   2^n-3 (https://www.mersenneforum.org/showthread.php?t=26170)

paulunderwood 2020-11-07 06:39

2^n-3
 
How easy would it be to alter gpuOwl to crunch 2^n-3?

Is the current gpuowl.cl hackable to do this? If so what needs to be changed? Is it just a matter of hacking the carry code?

axn 2020-11-07 06:47

[QUOTE=paulunderwood;562515]Is it just a matter of hacking the carry code?[/QUOTE]
Doubtful. With +/-1 you get the mod for free as a result of the IBDWT itself. Not sure what additional thing needs to be done to do the same for -3.

preda 2020-11-07 07:04

[QUOTE=paulunderwood;562515]How easy would it be to alter gpuOwl to crunch 2^n-3?

Is the current gpuowl.cl hackable to do this? If so what needs to be changed? Is it just a matter of hacking the carry code?[/QUOTE]

One problem is that gpuowl.cl is very heavily optimized for the "-1" case -- the weighting/unweighting. A lot of tricks have been applied in that area. To change, a logical approach would be to unoptimize (i.e. produce clean & slow code, that can be checked to be correct), then implement the new functionality, then optionally reoptimize the new code.

Another approach is to start from a clean-slate, and import blocks from gpuowl.cl if/when they prove useful.


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