It is very true that I am not familiar with geng, nor sagemath. I just installed on my machine a few days ago.
The reason I want to modify geng.c is I don't have a way to partition the output of "geng 12". I have finished up to "geng 11" so far, mostly with manual work. I know how many "geng 12" generates. With "geng 12", the output, if written to a file, is too large for my machine to handle. I can write to about 300G, not anything like 1500G. That is why I am looking at res/mod, but it seems I can't easily control how large the output will be (or I just don't know how). So if I can modify "geng" program, I can control the output range. Any other suggestion? On Friday, March 22, 2019 at 12:28:32 AM UTC-7, nvcleemp wrote: > > Why would you want to modify geng.c? From your previous comments I get the > impression that you are not familiar with the algorithm that geng uses. > You're not even familiar with the way geng encodes graphs. In that case it > is almost guaranteed that you will break something if you modify it. > > So again, why would you want to modify it? If it is to obtain an even > split, then you can only do this by generating all graphs and then > splitting the output. The commands to do this without translating the > intermediate graphs to the Sage data structure have been shown in the other > thread. For anything larger than 12 this will still be too slow since there > are just so many graphs. > > The builtin splitting in geng works by generating the graphs and at a > certain depth in the generation tree counting the branches and only > proceeding if the number modulo mod is equal to res. This way not > everything is generated and if this is done at a suitable depth then the > splitting will be fairly equal. > > Cheers > Nico > > Op vr 22 mrt. 2019 om 06:06 schreef Ai Bo <boai...@gmail.com <javascript:> > >: > >> Sorry for not being clear. >> I meant I used geng —help. >> Apparently, the equal divide doesn’t help in my example case. >> Where is this geng.c file? If I modify geng.c, how should I build geng? >> >> On Thu, Mar 21, 2019 at 9:58 PM John H Palmieri <jhpalm...@gmail.com >> <javascript:>> wrote: >> >>> >>> >>> On Thursday, March 21, 2019 at 9:38:03 PM UTC-7, Ai Bo wrote: >>>> >>>> Saw this in the document: >>>> res/mod : only generate subset res out of subsets 0..mod-1 >>>> >>> >>> It would help if you gave some context for this. I'm guessing that most >>> Sage users won't know what "geng" is. I certainly didn't. I found by >>> searching the source code that you found this help message in the method >>> "nauty_geng" in graph_generators.py: you should have said this at the start >>> instead of just "saw this in the document". This makes it look like the >>> program "geng" comes from nauty. Now look at the nauty source code (there >>> is a tar file in the "upstream" directory, if you have a source code >>> version of Sage, also available at >>> http://files.sagemath.org/spkg/upstream/nauty/index.html). The nauty >>> manual says >>> >>> res/mod : only generate subset res out of subsets 0..mod-1 >>> >>> and >>> >>> See program text for much more information. >>> >>> The file geng.c says >>> >>> mod, res = a way to restrict the output to a subset. >>> All the graphs in G(n,mine..maxe) are divided >>> into >>> disjoint classes C(0,mod),C(1,mod),...,C(mod-1, >>> mod), >>> of very approximately equal size. >>> Only the class C(res,mod) is written. >>> >>> If the -x or -X switch is used, they must have >>> the >>> same value for different values of res; >>> otherwise >>> the partitioning may not be valid. In this case >>> (-x,-X with constant value), the usual >>> relationships >>> between modulo classes are obeyed; for example >>> C(3,4) = C(3,8) union C(7,8). This is not true >>> if 3/8 and 7/8 are done with -x or -X values >>> different from those used for 3/4. >>> >>> >>> >>>> >>>> How is the output divided? >>>> >>>> I tried with : ../sage-8.6/local/bin/geng 6 -C 0/7 >>>> and then I iterated from 0/7, 1/7, 2/7, 3/7.... >>>> Why the output is 27, 21, 7, 1, 0, 0, ... >>>> >>>> How is the subset generated? >>>> >>>> Thank you. >>>> >>> -- >>> You received this message because you are subscribed to a topic in the >>> Google Groups "sage-devel" group. >>> To unsubscribe from this topic, visit >>> https://groups.google.com/d/topic/sage-devel/FJZoODSZK3Q/unsubscribe. >>> To unsubscribe from this group and all its topics, send an email to >>> sage-devel+...@googlegroups.com <javascript:>. >>> To post to this group, send email to sage-...@googlegroups.com >>> <javascript:>. >>> Visit this group at https://groups.google.com/group/sage-devel. >>> For more options, visit https://groups.google.com/d/optout. >>> >> -- >> You received this message because you are subscribed to the Google Groups >> "sage-devel" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to sage-devel+...@googlegroups.com <javascript:>. >> To post to this group, send email to sage-...@googlegroups.com >> <javascript:>. >> Visit this group at https://groups.google.com/group/sage-devel. >> For more options, visit https://groups.google.com/d/optout. >> > -- You received this message because you are subscribed to the Google Groups "sage-devel" group. 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