Go Back > Factoring Projects > Factoring

Thread Tools
Old 2005-08-25, 00:11   #1
R.D. Silverman
R.D. Silverman's Avatar
"Bob Silverman"
Nov 2003
North of Boston

165108 Posts
Unhappy Interesting Screw-up

The linear algebra just finished on 2,969+ and it failed to find any true
dependencies. It did find 64 pseudo dependencies.

I just found out why.

The filtering first does two passes, looking at
the number of excess relations after the first pass to adjust parameters
for the second.

The output files only contain primes above a certain threshold (typically
250k). It is therefore necessary to completely factor all relations before
doing a final filter pass and then building/solving the matrix.

Apparently, something caused the re-factor to fail. I suspect a power failure
in the middle of the computation.

I failed to notice that it had failed, and started up the final filter pass.
Therefore the final matrix only contained primes greater than 250K. Ooops!

I am re-doing the entire process now.

Maybe this will teach me to be more careful.
R.D. Silverman is offline   Reply With Quote
Old 2005-08-25, 01:21   #2
sean's Avatar
Aug 2004
New Zealand

23010 Posts

You have my sympathy.

Unfortunately, you can be almost certain that something similar will happen in the future. It's pretty hard to get everything right all the time.

When I did a C147 last year, I similarly wasted 20+ days solving a matrix that turned out to be broken. The cause ended up being a corrupt file left over from a machine crash that the filtering stage had picked up and included. It took me a while to track the cause down.
sean is offline   Reply With Quote
Old 2005-08-25, 08:44   #3
xilman's Avatar
May 2003
Down not across

2×5,791 Posts

Originally Posted by R.D. Silverman
The linear algebra just finished on 2,969+ and it failed to find any true
dependencies. It did find 64 pseudo dependencies.


I am re-doing the entire process now.

Maybe this will teach me to be more careful.
Been there, done that.

When NFSNET factored 2,811- the dataset was so large I had serious problems filtering. One problem arose from a bug in Windows' IO library -- after reading more than 4G of text files (WIndows distinguishes between text and data) it lost track of where the line endings (CRLF on Windows, contrast with CR on MacOS and LF on Unices). The relations files became subtly corrupted and I was unable to build a "small" matrix. In desperation, I ran an enormous but very sparse matrix on the cluster. I forget the details, but it ran for a long time on a 32-cpu cluster, only to produce useless dependencies.

xilman is offline   Reply With Quote
Old 2005-08-25, 15:48   #4
VJS's Avatar
Dec 2004

13·23 Posts


May I ask you:
- how long the entire process took
- Computers
- HD space
- memory requirements

2,969+ seems pretty big...
VJS is offline   Reply With Quote

Thread Tools

Similar Threads
Thread Thread Starter Forum Replies Last Post
Some interesting patterns regarding mod CuriousKit Miscellaneous Math 24 2015-04-06 18:40
An interesting series Citrix Math 0 2005-11-02 05:33
A new interesting thing about 15k robert44444uk 15k Search 0 2005-04-06 23:00
very interesting reading stippix Hardware 0 2004-09-27 06:19
Something Interesting clowns789 Hardware 1 2003-12-20 12:36

All times are UTC. The time now is 04:09.

Mon Dec 5 04:09:39 UTC 2022 up 109 days, 1:38, 0 users, load averages: 1.49, 1.22, 0.99

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2022, Jelsoft Enterprises Ltd.

This forum has received and complied with 0 (zero) government requests for information.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation.
A copy of the license is included in the FAQ.

โ‰  ยฑ โˆ“ รท ร— ยท โˆ’ โˆš โ€ฐ โŠ— โŠ• โŠ– โŠ˜ โŠ™ โ‰ค โ‰ฅ โ‰ฆ โ‰ง โ‰จ โ‰ฉ โ‰บ โ‰ป โ‰ผ โ‰ฝ โŠ โŠ โŠ‘ โŠ’ ยฒ ยณ ยฐ
โˆ  โˆŸ ยฐ โ‰… ~ โ€– โŸ‚ โซ›
โ‰ก โ‰œ โ‰ˆ โˆ โˆž โ‰ช โ‰ซ โŒŠโŒ‹ โŒˆโŒ‰ โˆ˜ โˆ โˆ โˆ‘ โˆง โˆจ โˆฉ โˆช โจ€ โŠ• โŠ— ๐–• ๐–– ๐–— โŠฒ โŠณ
โˆ… โˆ– โˆ โ†ฆ โ†ฃ โˆฉ โˆช โŠ† โŠ‚ โŠ„ โŠŠ โŠ‡ โŠƒ โŠ… โŠ‹ โŠ– โˆˆ โˆ‰ โˆ‹ โˆŒ โ„• โ„ค โ„š โ„ โ„‚ โ„ต โ„ถ โ„ท โ„ธ ๐“Ÿ
ยฌ โˆจ โˆง โŠ• โ†’ โ† โ‡’ โ‡ โ‡” โˆ€ โˆƒ โˆ„ โˆด โˆต โŠค โŠฅ โŠข โŠจ โซค โŠฃ โ€ฆ โ‹ฏ โ‹ฎ โ‹ฐ โ‹ฑ
โˆซ โˆฌ โˆญ โˆฎ โˆฏ โˆฐ โˆ‡ โˆ† ฮด โˆ‚ โ„ฑ โ„’ โ„“
๐›ข๐›ผ ๐›ฃ๐›ฝ ๐›ค๐›พ ๐›ฅ๐›ฟ ๐›ฆ๐œ€๐œ– ๐›ง๐œ ๐›จ๐œ‚ ๐›ฉ๐œƒ๐œ— ๐›ช๐œ„ ๐›ซ๐œ… ๐›ฌ๐œ† ๐›ญ๐œ‡ ๐›ฎ๐œˆ ๐›ฏ๐œ‰ ๐›ฐ๐œŠ ๐›ฑ๐œ‹ ๐›ฒ๐œŒ ๐›ด๐œŽ๐œ ๐›ต๐œ ๐›ถ๐œ ๐›ท๐œ™๐œ‘ ๐›ธ๐œ’ ๐›น๐œ“ ๐›บ๐œ”