20160729, 20:29  #1 
(loop (#_fork))
Feb 2006
Cambridge, England
1936_{16} Posts 
"error: unexpected dense ideal found"
On two attempts when I've tried to process C250_146_80, I get this message
Code:
commencing linear algebra read 11969669 cycles cycles contain 39115759 unique relations read 39115759 relations using 20 quadratic characters above 4294917296 building initial matrix error: unexpected dense ideal found 
20160729, 22:53  #2 
(loop (#_fork))
Feb 2006
Cambridge, England
2×7×461 Posts 
"run svn update more than once every thirty months" seems likely to be a sensible place to start
I'd have expected sort u on a 60GB file stored on NVMe SSD to take less than four hours. Code:
grep "[09]*,[09]*:[09afAF,]*:[09afAF,]*" msieve.dat  sort u t: k1 T .  tee msieve.dat.u  wc l Last fiddled with by fivemack on 20160729 at 22:55 
20160731, 01:04  #3 
Tribal Bullet
Oct 2004
3^{2}·5·79 Posts 
Never seen a problem in this neighborhood before. Basically a relation has an ideal below 100 that doesn't appear in the factor base.

20160807, 13:46  #4 
(loop (#_fork))
Feb 2006
Cambridge, England
2×7×461 Posts 
svn 993 still shows the problem. I've deduplicated the input file and removed two relations which had a few hundred zero bytes in the middle of the line, and am trying again; I wonder if
Code:
38236219,1450370:23a12b0f,d1c8219d,3ad5,8~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~1736033,521561:1a03,1391,3bf4229,e9abb9,8a650f,2ea3d1,523bb,2c825:38671d35,dc65ae9d,195acf9,88d35 
20160807, 14:40  #5 
Tribal Bullet
Oct 2004
3^{2}·5·79 Posts 
There wouldn't be a comma or ':' after the 8, so I would assume the relation was rejected.
Would it make sense to instrument the relation whose text caused the error? 
20160808, 06:07  #6 
(loop (#_fork))
Feb 2006
Cambridge, England
1936_{16} Posts 
Adding a few obvious printfs, I am even more confused now:
Code:
error: unexpected dense ideal found: prime 0, address 0x7ffdf212e4c0, p_lo 0 p_hi 0 r_lo 1 r_hi 0 Cycle number 69798 c=0x7f20981ee4d0 c>weight=0 c>cycle.num_relations=1 This doesn't seem to be a fragile bug, it's happening however I manipulate the dataset, but it might be awkward for you to download the 35GB data locally. There is a slight peculiarity about the polynomial here, which is that c6 and c0 are not only both squares but also both divisible by 4. 
20160808, 14:58  #7 
Tribal Bullet
Oct 2004
6743_{8} Posts 
If it's a side effect of malformed relation text we could try to work backwards to the savefile line that causes it. In that neighborhood of code, variable 'c' is an la_col_t structure defined in include/common.h:281; the 'cycle' field of that structure gives the indexes into the list of relation_t structures given by 'rlist'. relation_t is defined in gnfs/gnfs.h:326, the most useful information there will be the relation 'a' value which can pinpoint the savefile line that's involved. The list of factors in a relation_t structure is runlengthencoded to save space, and it's possible the decompression messes up.
If you have the .mat file then you can skip the very slow matrix build phase with 'skip_matbuild=1' in the NFS commandline arguments, to go straight to reading the matrix in from disk. 
20160808, 17:05  #8  
Bamboozled!
"๐บ๐๐ท๐ท๐ญ"
May 2003
Down not across
2·3·29·67 Posts 
Quote:
Quote:


20160808, 21:55  #9  
(loop (#_fork))
Feb 2006
Cambridge, England
14466_{8} Posts 
Quote:
Code:
(gdb) print c $1 = (la_col_t *) 0x7fffdff004d0 (gdb) print *c $2 = {data = 0x0, weight = 0, cycle = {num_relations = 1, list = 0x8ddac0}} (gdb) print c>cycle $3 = {num_relations = 1, list = 0x8ddac0} (gdb) print c>cycle.list $4 = (uint32 *) 0x8ddac0 (gdb) print *(c>cycle.list) $5 = 5666740 (gdb) print rlist[5666740] $6 = {a = 13511, b = 8949, rel_index = 988992, num_factors_r = 9 '\t', num_factors_a = 8 '\b', factors = 0x3bc766f0 "\t\216+}{\204\065,P\204\071o,\204%X\030\202u}\220\005K\211q\201\202A'b\206m#\252ir\034\217\202\215\251\331", <incomplete sequence \341>} (gdb) x/24x rlist[5666740].factors 0x3bc766f0: 0x7d2b8e09 0x2c35847b 0x6f398450 0x5825842c 0x3bc76700: 0x7d758218 0x894b0590 0x8281712d 0x86622741 0x3bc76710: 0x69aa236d 0x828f1c72 0xe1d9a98d 0x00000000 0x3bc76720: 0x00000000 0x00000000 0x00000051 0x00000000 0x3bc76730: 0x946fb037 0x5a6b921d 0x50458a27 0x791f8334 0x3bc76740: 0x1e2d8252 0x810c1382 0x09d98582 0x79870b81 butternut@butternut:/scratch/C250_146_80$ grep "^13511," msieve.dat 13511,10301208:503bb4c1,3234c4f3,af1,92ed87b,216cc5,3e1ef:24a244b9,1eadc45,c2551d,39a7a5,2327ed,13649 13511,8949:709,9EFEAB,941635,8B37B9,462C25,43EF5,26585,78AD:D893C1,A91ED,1E73969 13511,91882855:ac1ad489,6c7954d,6640813,a8faff,511405,4b911,d711:2b1003bd,b5e135d,335fea9,274bb95,10b02e9,8fe25,4f6d ? f(x,y)=21316*y^6+100*x^6 ? g(x,y)=9444732965739290427392000000000000000000000000*y+13695791164569918553628942336*x ? factor(f(13511,8949)) %10 = [2 3] [13 1] [41 1] [89 1] [97 1] [692717 1] 0xA91ED [14193601 1] 0xD893C1 [31930729 1] 0x1E73969 ? factor(g(13511,8949)) %11 = [2 13] [1801 1] 0x709 [30893 1] 0x78AD [157061 1] 0x26585 [278261 1] 0x43EF5 [4598821 1] 0x462C25 [9123769 1] 0x8B37B9 [9705013 1] 0x941635 [10419883 1] 0x9EFEAB Hope this is useful. Proceeding in a trythingsandseewhathappens way, I've deleted the lines with a=13511 from msieve.dat, revised the msieve.fb to remove the common factors from A0 and A6 and from R0 and R1, and am rerunning overnight. Last fiddled with by fivemack on 20160808 at 22:59 

20160808, 23:38  #10 
Basketry That Evening!
"Bunslow the Bold"
Jun 2011
40<A<43 89<O<88
16065_{8} Posts 
Wouldn't it be more informative to do these things one at a time? Of course it might be prohibitively untimely.

20160809, 19:32  #11  
Tribal Bullet
Oct 2004
3^{2}×5×79 Posts 
Quote:
Any factors of relations that are less than 100 are completely ignored by the filtering, which explains why you had to get to the LA to see anything wrong. Last fiddled with by jasonp on 20160809 at 19:35 

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