20180121, 14:35  #1 
Jan 2018
11 Posts 
Resume linear algebra
I used Brian Gladman's python script which uses GGNFS and MSIEVE to factor 155 digit number, but it threw errors when it came to linear algebra step (I assumed it was because of RAM), so I moved it to another machine with more RAM.
When I ran the script there, it started sieving from beginning (so the .dat file was removed). Do I have to run some command from cmd to resume linear algebra step? By the way, I followed this guide. 
20180121, 17:09  #2 
Sep 2009
3^{2}×5×53 Posts 
If you still have the .dat file somewhere, eg on the original machine, you can probably restart linear algebra (you may have to rebuild the matrix though). If you have lost the .dat file you will have to rerun the whole job. Make a backup copy of the .dat file (and everything else in the directory) before you start experimenting though.
Can you post the log from the failing run so we can see what went wrong. Also a directory listing of where you were running it. You probably need to rerun the msieve step in the log, replacing nc2 with ncr, if you have all the files from the failing attempt at linear algebra. If that fails try running msieve with nc to rebuild the matrix. I assume you are running Windows from your mention of running things under cmd. What version is it though? Chris Last fiddled with by chris2be8 on 20180121 at 17:14 Reason: Clarify to back up every related file. 
20180121, 18:32  #3 
"Victor de Hollander"
Aug 2011
the Netherlands
3^{2}·131 Posts 
Without the relations and the matrix you can't finish the factorization. You need the matrix to resume linear algebra (ncr to resume or nc2 to rebuild) and the relations in the sqr fase (nc3).
Last fiddled with by VictordeHolland on 20180121 at 18:33 
20180121, 19:25  #4 
Basketry That Evening!
"Bunslow the Bold"
Jun 2011
40<A<43 89<O<88
3×29×83 Posts 
The important part is that ncr is required to resume. Without ncr you will overwrite the data, sadly. More than one forum user has lost an in progress matrix in this manner before

20180121, 20:04  #5 
"Ed Hall"
Dec 2009
Adirondack Mtns
2^{3}×607 Posts 
But, if he didn't rerun on the original machine, the relations should still exist there. The OP would also need the original poly file, or fb, IIRC. On the original machine, there should be a compressed file with all the original relations, too.
Or, is my memory really bad, or the comparison between Win and linux too far removed? 
20180121, 21:19  #6 
"Victor de Hollander"
Aug 2011
the Netherlands
3^{2}·131 Posts 
The dir should look something like this on Windows (note this is an old dir)
Code:
18042016 18:47 12.761.511.205 C204_119_99.dat.gz 30122015 22:47 99.223 Changes 31122015 22:45 864.110 libmsieve.a 11092015 01:38 56.978 libwinpthread1.dll 31122015 22:45 3.175.900 msievesvn988x64sandybridge.exe 22042016 01:13 23.917.535.851 msieve.dat 29042016 06:01 570.056.176 msieve.dat.bak.chk 29042016 07:03 570.056.176 msieve.dat.chk 23042016 00:51 509.858.000 msieve.dat.cyc 29042016 07:36 114.010.464 msieve.dat.dep 23042016 00:51 6.132.670.652 msieve.dat.mat 18042016 15:21 429 msieve.fb 18042016 15:21 502 msieve.poly 11092014 14:01 185.976 pthreadGC2.dll 11092014 14:01 82.944 pthreadVC2.dll 30122015 22:47 25.290 Readme 30122015 22:47 57.946 Readme.nfs 30122015 22:47 7.987 Readme.qs 18042016 15:21 205 worktodo.ini 17082015 17:19 90.250 zlib1.dll 
20180122, 15:43  #7 
Jan 2018
1011_{2} Posts 
Hi, I'm sorry for the late reply.
The problem is, this script ran on a really bad virtual machine, which has 4GB RAM and 4 core CPU with 1 thread each. Windows already used 50% of RAM so I guess msieve didn't have enough memory to complete linear algebra. I have Windows 2012 R2 by the way. So, the minute I stopped the linear algebra step, I saved everything. I attached 2 pictures that show all files (it's zipped, so I couldn't ls it through cmd). The full log is in attachments. 
20180122, 15:54  #8 
I moo ablest echo power!
May 2013
2^{2}·11·41 Posts 
What RSA number are you trying to break?

20180122, 17:09  #9 
Jan 2018
11 Posts 
This one:
1772352223689553499523382657591107586734440334822954296365208356693849378633858324876899946660923527875550194354495596668114847388151261943936272297881447 (154 digits) 
20180122, 17:10  #10 
Sep 2009
3^{2}×5×53 Posts 
I only use Linux, so I'm guessing a bit. But try the following after extracting the files onto another system:
msieve s .\rsa/rsa.dat l .\rsa/rsa.log i .\rsa/rsa.ini nf .\rsa/rsa.fb t 4 ncr If that fails try restarting nc2 from scratch: msieve s .\rsa/rsa.dat l .\rsa/rsa.log i .\rsa/rsa.ini nf .\rsa/rsa.fb t 4 nc2 If either of those worked then run: msieve s .\rsa/rsa.dat l .\rsa/rsa.log i .\rsa/rsa.ini nf .\rsa/rsa.fb t 4 nc3 But if they both failed try rebuilding the matrix (this will try to run all msieve steps in one go): msieve s .\rsa/rsa.dat l .\rsa/rsa.log i .\rsa/rsa.ini nf .\rsa/rsa.fb t 4 nc Obviously keep the backup zip files safe until you have factored the number. If you run: msieve h you will get a brief summary of what options msieve accepts. That should help you work out what it wants (eg after l put the name of the log file. Chris 
20180122, 18:11  #11 
Jan 2018
11 Posts 
I ran (added verbose too)
msieve v s .\rsa/rsa.dat l .\rsa/rsa.log i .\rsa/rsa.ini nf .\rsa/rsa.fb t 4 ncr and it threw an error: cannot open matrix checkpoint file, so I guess that won't work. Tried the nc2, it built the matrix and is now performing linear algebra, BUT I get these errors: lanczos halted after x iterations (dim = x) linear algebra failed; retrying memory use: 868.8 MB lanczos error: submatrix is not invertible Those were the same errors as on the virtual machine, I thought they were because of memory, but I have 16 GB of RAM here... Is this normal? By the way, I'm using the same .dat and .dat.cyc. 
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