Discussion related to cado-nfs

[Phil Pemberton <philpem@philpem.me.uk>]

I've just had a several-day 512-bit compute finish with what appears to 
be a fatal error.

The compute setup was --
  Server - Xeon E3-1270 8-core 3.5GHz, 16GB RAM, 250GB SSD
  Clients -
    Xeon server running client threads - as above
    Intel i5-9400 6-core 2.9GHz, 16GB RAM, 2TB hard drive
    Intel i5-3570K 4-core 3.4GHz, 8GB RAM, 2TB hard drive
    AMD Ryzen 5 3600X 6-core, 16GB RAM, 500GB hard drive


OS in use was a mix of Linux Mint 20 or Ubuntu 20.04 LTS.


Here are the last lines of the error log:


Info:Quadratic Characters: Starting
Info:Quadratic Characters: Total cpu/real time for characters: 
175.98/52.0178
Info:Square Root: Starting
Info:Square Root: Creating file of (a,b) values
Warning:HTTP server: 127.0.0.1 code 410, message Distributed computation 
finished
Warning:HTTP server: 127.0.0.1 code 410, message Distributed computation 
finished
Warning:Command: Process with PID 1730797 finished with return code -9
Error:Square Root: Program run on server failed with exit code -9
Error:Square Root: Command line was: 
/home/philpem/cado-nfs/build/uncia/sqrt/sqrt -poly 
/home/philpem/cado-nfs/workdir/c150.poly -prefix 
/home/philpem/cado-nfs/workdir/c150.dep.gz -dep 0 -t 8 -side0 -side1 
-gcd > /home/philpem/cado-nfs/workdir/c150.sqrt.stdout.4 2> 
/home/philpem/cado-nfs/workdir/c150.sqrt.stderr.4
Error:Square Root: Stderr output (last 10 lines only) follow (stored in 
file /home/philpem/cado-nfs/workdir/c150.sqrt.stderr.4):
Error:Square Root:      Alg(5): fragment 1/64 of level 00 done by thread 
0 at wct=267.54s
Error:Square Root:      Alg(4): fragment 1/64 of level 00 done by thread 
0 at wct=267.66s
Error:Square Root:      Alg(2): fragment 25/64 of level 00 done by 
thread 3 at wct=267.81s
Error:Square Root:      Alg(2): fragment 17/64 of level 00 done by 
thread 2 at wct=268.02s
Error:Square Root:      Alg(2): fragment 1/64 of level 00 done by thread 
0 at wct=268.75s
Error:Square Root:      Alg(1): fragment 34/64 of level 00 done by 
thread 4 at wct=299.10s
Error:Square Root:      Alg(1): fragment 18/64 of level 00 done by 
thread 2 at wct=299.18s
Error:Square Root:      Alg(1): fragment 10/64 of level 00 done by 
thread 1 at wct=300.55s
Error:Square Root:      Alg(1): fragment 26/64 of level 00 done by 
thread 3 at wct=300.92s
Error:Square Root:
Traceback (most recent call last):
  File "./cado-nfs.py", line 202, in <module>
    factors = factorjob.run()
  File "/home/philpem/cado-nfs/./scripts/cadofactor/cadotask.py", line 
6131, in run
    last_status = task.run()
  File "/home/philpem/cado-nfs/./scripts/cadofactor/cadotask.py", line 
5045, in run
    raise Exception("Program failed")
Exception: Program failed


Server command line:

./cado-nfs.py NUMBER_REDACTED server.whitelist=0.0.0.0/0 --server 
--workdir $PWD/workdir

Client command line:

./cado-nfs-client.py --basepath $PWD/wdir 
--server=https://SERVERNAME:36485 --certsha1=CERTSHA_REDACTED --bindir 
$(eval `make show` ; echo $build_tree) --override -t 8

The "-t" parameter was set to the number of physical cores on the system.


Can anyone explain to me --

  What has gone wrong here? Have I hit a bug?

  Is the failed factorisation recoverable?

  What can I do to avoid this in future?


CADO-NFS version is Git commit c5b20eac12ea225a325d582923ef058832cda28e, 
same on all machines.

Thanks.
--
Phil.
philpem@philpem.me.uk
https://www.philpem.me.uk/