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-   -   Weird segfault and "fix"? (https://www.mersenneforum.org/showthread.php?t=26335)

Xyzzy 2020-12-24 00:39

Weird segfault and "fix"?
 
2 Attachment(s)
We have used the same binary for Msieve for a very long time. We think we compiled it with a Debian system a long time ago.

It has always worked perfectly.

It worked today, on a big job, on our Debian 10 Asus "NUC".

But today, trying that big job on our Fedora 33 system, it segfaulted.[CODE]$ uname -a
Linux vi 5.9.15-200.fc33.x86_64 #1 SMP Wed Dec 16 19:14:35 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux[/CODE][CODE]$ ./msieve -nc -p -t 1 -v

Msieve v. 1.54 (SVN 1030)
Wed Dec 23 18:03:00 2020
random seeds: bd3abf07 7d0d8f6d
factoring 146994713613685430462560633054030708553424988945059235528485114251973128261237846710634754720664533019191816640360086976564413805312241389512020336099540339919422287150716423619360302926533658867136193404152798094989961139809454759339483042766147 (246 digits)
no P-1/P+1/ECM available, skipping
commencing number field sieve (246-digit input)
R0: 135637000670178176410246734932581577148578721
R1: -511324276025564512546607
A0: 201770283
A1: 0
A2: 0
A3: 0
A4: 0
A5: 0
A6: 1
skew 24.22, size 9.679e-14, alpha 0.121, combined = 2.205e-14 rroots = 0

commencing relation filtering
estimated available RAM is 32080.8 MB
commencing duplicate removal, pass 1
Segmentation fault (core dumped)[/CODE]Strangely, it would work for a simple factorization.[CODE]$ ./msieve -v 115367564564210182766242534110944507919869313713243756429

Msieve v. 1.54 (SVN 1030)
Wed Dec 23 18:06:25 2020
random seeds: e6d43db7 503bfdc1
factoring 115367564564210182766242534110944507919869313713243756429 (57 digits)
p7 factor: 3387679
p50 factor: 34055046113935288073705488067477617542827792631251
elapsed time 00:00:00[/CODE]So we recompiled it using the development tools on the Fedora system and now it works.[CODE]$ ./msieve -nc -p -t 1 -v

Msieve v. 1.54 (SVN 1035M/VBITS=64/Xyzzy)
Wed Dec 23 18:00:45 2020
random seeds: 7a64fe17 6d8eca8e
factoring 146994713613685430462560633054030708553424988945059235528485114251973128261237846710634754720664533019191816640360086976564413805312241389512020336099540339919422287150716423619360302926533658867136193404152798094989961139809454759339483042766147 (246 digits)
no P-1/P+1/ECM available, skipping
commencing number field sieve (246-digit input)
R0: 135637000670178176410246734932581577148578721
R1: -511324276025564512546607
A0: 201770283
A1: 0
A2: 0
A3: 0
A4: 0
A5: 0
A6: 1
skew 24.22, size 9.679e-14, alpha 0.121, combined = 2.205e-14 rroots = 0

commencing relation filtering
estimated available RAM is 32080.8 MB
commencing duplicate removal, pass 1
^C
received signal 2; shutting down[/CODE]Why?

Here is all we could find WRT errors:[CODE][ 161.774741] msieve[3252]: segfault at 7fd580928500 ip 000055a6fcfb4dbd sp 00007ffd946d2ee0 error 7 in msieve[55a6fcf9c000+a9000]
[ 161.774749] Code: 56 4c 8d b9 98 00 00 00 41 55 41 54 49 89 cd 55 53 48 89 fd 48 83 ec 08 48 85 f6 8b 19 0f 88 b2 00 00 00 48 8b 81 a0 00 00 00 <48> 89 30 0f 95 c0 0f b6 c0 89 81 9c 00 00 00 4d 8d a5 a8 00 00 00[/CODE]FWIW, the [C]msieve.dat[/C] file (42GB) is not compressed and all duplicates and bad relations have been removed from it.

:help:

EdH 2020-12-24 00:53

It might be because there was some Msieve code that didn't play 100% with GMP-6.2.0. Jasonp has since fixed that, so the latest code should be fine. Which GMP is on which machine?

Xyzzy 2020-12-24 01:30

Is this the right information?

[C]Debian 10
libgmp-dev
libgmp-dev_6.1.2+dfsg-4_amd64.deb[/C]

[C]Fedora 33
gmp-devel.x86_64
gmp-6.2.0-5.fc33.src.rpm[/C]

EdH 2020-12-24 03:40

[QUOTE=Xyzzy;567181]Is this the right information?

[C]Debian 10
libgmp-dev
libgmp-dev_6.1.2+dfsg-4_amd64.deb[/C]

[C]Fedora 33
gmp-devel.x86_64
gmp-6.2.0-5.fc33.src.rpm[/C][/QUOTE]
I would think it was the new GMP-6.2.0 and it looks like you have a later checkout (1035) for Msieve now. You should be good.

If you want to see some details, you can look at (and around) [URL="https://www.mersenneforum.org/showpost.php?p=540947&postcount=81"]this post[/URL] in my YAFU "How I ..." thread

Xyzzy 2020-12-24 13:38

:tu:


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