20060309, 11:56  #1 
"Bob Silverman"
Nov 2003
North of Boston
16510_{8} Posts 
CWI Matrix Solver
Hi,
Has anyone else ever encountered an error from the CWI solver that says "too many orthogonal vectors" near the very end of the computation? I just got this message while doing the LA for 2,815. It is possible that I have some kind of memory/hardware problem. This is the second time I have seen this. The last time I refiltered the data, reran the solver and things were fine. Last night I tried backing up the computation to the last saved checkfiles, but still had the same problem at the end. I did some memory diagnostics with the BIOS, but turned up nothing. Tonight, I will modify the software to ignore the condition and continue the computation anywhere, but I do not expect success. I will burn a CD, transfer the data to another machine and try rerunning with the same matrix, rather than refiltering. This will tell me if it is likely a software bug or a hardware problem. But I will have to wait another 8 days for the result. Ideas, anyone? 
20060310, 02:19  #2  
"William"
May 2003
New Haven
3·7·113 Posts 
Quote:


20060310, 13:42  #3  
"Bob Silverman"
Nov 2003
North of Boston
1110101001000_{2} Posts 
Quote:
data. If it succeeds, I will know that I have a hardware problem and look into it further. When not solving matrices my NFS code runs constantly (both threads) on the machine that is having problems. This code makes heavy use of memory, yet it has never had a problem. And it tortures the processor as well. I was wondering if anyone else had ever encountered this problem. 

20060314, 13:09  #4  
Bamboozled!
"๐บ๐๐ท๐ท๐ญ"
May 2003
Down not across
2D34_{16} Posts 
Quote:
The only practical solution we ever found was to refilter and produce a slightly different matrix. I will be slightly surprised if subsequent runs produce a different and more useful answer. If it does, it may be an indication that the initial random vectors chosen at the start of the algorithm turned out not to be useful. I don't remember whether I've ever seen that happen in practice. Paul Last fiddled with by xilman on 20060314 at 13:09 

20060314, 14:01  #5  
"Bob Silverman"
Nov 2003
North of Boston
2^{3}×937 Posts 
Quote:
The matrix has 3392K rows and 3395K columns.. Very nearly square. The same matrix is now running on a different machine. It will finish Saturday. 

20060314, 15:05  #6  
"Bob Silverman"
Nov 2003
North of Boston
1D48_{16} Posts 
Quote:
have the same problem as the first? Will switching machines solve the problem? N.B. I would hate to have to reformulate the matrix and do the reduction yet another time..... Meanwhile, filtering for 2,833+ is nearly done and sieving for 2,1406M is in progress. 

20060319, 17:56  #7  
"Bob Silverman"
Nov 2003
North of Boston
1D48_{16} Posts 
Quote:
It had prime factors of 57,67, and 72 digits. 

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