Discussion related to cado-nfs

[Paul Leyland <paul.leyland@gmail.com>]

I, and I believe, many others have been bitten by this misfeature. May I 
suggest that the default be reduced to one or two threads?  A comment in 
big friendly letters could be added to the effect that raising the 
argument to -t can be made if oodles of RAM is available.

Paul (the other one)

On 30/05/2025 08:04, Paul Zimmermann wrote:
>         Hi David,
>
> it might be that the square root took too much memory for your computer.
> You can try to run each square root by hand. In your log file you should
> have a command like this:
>
> /home/ubuntu/cado-nfs/build/ip-172-31-39-108/sqrt/sqrt -poly nfsdata/c110.poly 
> -prefix nfsdata/c110.dep.gz -dep 0 -t 8 -side0 -side1 -gcd > 
> nfsdata/c110.sqrt.stdout.2 2> nfsdata/c110.sqrt.stderr.2
>
> Replace -t 8 (using 8 threads) by -t 1 and run the command by hand.
>
> In the out file, you should get the square root on the rational side Rat(0)
> as below, and that for the algebraic side Alg(0) (which was killed).
> Then take the gcd of the difference Rat(0)-Alg(0) with N.
>
> If dependency 0 does not work, try with dependency 1 (-dep 1 -t 1).
>
> Paul
>
> > Date: Thu, 22 May 2025 06:21:00 -0400
> > From: David Bernier <david250@videotron.ca>
> >
> > Dear Cado-NFS list subscribers,
> >
> > On May 20, after a 5-day run of progress (including sieving and Linear
> > Algebra phases completed successfully),
> > a process was killed in the Square Root stage.
> >
> > I'm thinking of giving the factoring job another try. I'd like to know
> > what I should do differently
> > in the second try?
> >
> > I'm enclosing some console output obtained by "re-running" Cado-NFS
> > commands.
> >
> > Many thanks for your help,
> >
> > Yours sincerely,
> >
> > David Bernier
> >
> > P.S. I have the console that ran the job still active, so I can provide
> > more feedback/information.
> >
> > ---
> >
> >
> >
> > Summary: During the Square Root stage of NFS on a 156-digit number, a
> > process is/was unexpectedly killed.
> >
> >
> >
> > Number to factor:
> > 711184568226693729370734178977437454969661097325497188095372946030140070512120533859960933802665342317474945713448338045526414656892812610438356424893790777
> >
> > System: Windows 11, 14 physical cores, 32 Gb RAM
> >
> > Environment: Windows subsystem for Linux, Ubuntu OS.
> >
> > CADO-NFS version: May 15 INRIA Gitlab
> >
> >
> > Console output:
> > [...]
> >
> > Rat(1): level 7 took cpu=10.06s (wct=3.44s)
> > Rat(1): size of product = 1165873893 bits (peak 8183M)
> > Rat(1): starting rational square root at 217.92s (wct 23.16s)
> > Rat(0): level 7 took cpu=10.35s (wct=3.58s)
> > Rat(0): size of product = 1166172659 bits (peak 8183M)
> > Rat(0): starting rational square root at 218.96s (wct 23.51s)
> > Rat(2): computed square root at 246.29s (wct 32.91s)
> > Rat(2): reduced mod n at 246.65s (wct 33.04s)
> > Rat(2): computed g1^(nab/2) mod n at 246.65s (wct 33.04s)
> > Rat(2): square root is
> > 2989644409478105083184192941862416373829178248900748492033778468761708759940947400706710609583845143867705550622457684434372965541273518660603850655492329
> > Rat(2): square root time: 246.70s (wct 33.07s)
> > Rat(1): computed square root at 247.16s (wct 33.31s)
> > Rat(1): reduced mod n at 247.42s (wct 33.43s)
> > Rat(1): computed g1^(nab/2) mod n at 247.42s (wct 33.43s)
> > Rat(1): square root is
> > 42221083752672897432649835236878467298558925235196473407703932719285730039020916120352841273900764096331887321197946905478379591686774535795945618194989030
> > Rat(1): square root time: 247.44s (wct 33.46s)
> > Rat(0): computed square root at 247.72s (wct 33.78s)
> > Rat(0): reduced mod n at 247.81s (wct 33.90s)
> > Rat(0): computed g1^(nab/2) mod n at 247.81s (wct 33.90s)
> > Rat(0): square root is
> > 673519196366795654500627690739193337620391312598595525410540974165338799063212226861487610129250262216560246246273399961757622843656671620635565471957977684
> > Rat(0): square root time: 247.81s (wct 33.93s)
> > Alg(0): cannot seek in dependency file, using single-thread I/O
> > Alg(1): cannot seek in dependency file, using single-thread I/O
> > Alg(0): read 0 (a,b) pairs in 247.81s (wct 33.96s, peak 8183M)
> > Alg(2): cannot seek in dependency file, using single-thread I/O
> > [...]
> >
> > Alg(2): starting level 4 at cpu=1266.71s (wct=102.46s), 16 values to
> > multiply
> > Alg(1): level 4 took cpu=138.79s (wct=7.66s)
> > Alg(1): starting level 5 at cpu=1401.44s (wct=109.87s), 8 values to multiply
> > Alg(2): level 4 took cpu=139.62s (wct=7.69s)
> > Alg(2): starting level 5 at cpu=1406.33s (wct=110.15s), 8 values to multiply
> > Alg(0): level 4 took cpu=145.68s (wct=8.02s)
> > Alg(0): starting level 5 at cpu=1410.10s (wct=110.35s), 8 values to multiply
> > Alg(1): level 5 took cpu=146.35s (wct=8.95s)
> > Alg(1): starting level 6 at cpu=1547.79s (wct=118.82s), 4 values to multiply
> > Alg(2): level 5 took cpu=155.60s (wct=9.51s)
> > Alg(2): starting level 6 at cpu=1561.92s (wct=119.65s), 4 values to multiply
> > Alg(0): level 5 took cpu=152.15s (wct=9.32s)
> > Alg(0): starting level 6 at cpu=1562.25s (wct=119.67s), 4 values to multiply
> > Killed