:party:Three cheers for me - IDIOT OF THE DAY! First round of virtual beers on me. Will buy it with my GIMPS credits :grin:

I should have read my post before hitting the submit button. This GPU is in my home computer, and I couldn't remember what posts' exe I used when I posted from work.

I'm trying to run it on a GTS 450, cc 2.1. 64 bit Win 7 ultimate.

I did try the exe as in post 253, but it kept crashing. I used in a batch file:
ecm_gpu_4096 -v -gpu -gpucurves 200 10000 0 < input.txt

So instead I used the exe as in post 220. Same batch file format. The batch file runs to the end, but no factors found.

VBCurtis mentioned regular version. Where can I get it, or is it similar to post 220?

Adolf

Adolf-
At the top of post 275, note the first line of code uses "-savea" to save the end-of-stage1 checkpoints. The idea is that GPU-ECM runs stage 1 only, while old-fashioned ECM with -resume flag and the save file as input will run stage 2.

It may be that you are simply not finding any factors in stage 1 with B1=10000, and since you aren't saving the checkpoints, stage 2 is not being run.

Also, -gpucurves is used to override the setting ECM chooses for number of concurrent curves per run; I don't think you want to use this without a specific reason. Just use -c to control how many curves you want done; the program will adjust it to a multiple of the number of curves your GPU can handle at a time.

If you want to control the load on a GTS450 you should probably pick a multiple of 48 for the -gpucurves. The maximum for that card would be [B]192[/B], unless it's OEM in which case it's 144.

Don't know if anyone else is interested in this, but I've been playing around and see how high I can push the GPU-ECM. I'm currently at a 65530-bit version. It works fine using 2^64000-1 as a test number. Finds factors in stage 1 and 2.

[QUOTE=wombatman;379167]Don't know if anyone else is interested in this, but I've been playing around and see how high I can push the GPU-ECM. I'm currently at a 65530-bit version. It works fine using 2^64000-1 as a test number. Finds factors in stage 1 and 2.[/QUOTE]
I would be at least mildly surprised[sup]*[/sup] if you can't push it [b]much[/b] further. Whether it is worth doing is an entirely different matter.

Paul
* And would submit a bug report to Cyril

It is a highly composite number (think of the algebraic factorizations), so results on it would be dubious.

Try (2^63997-1)/383983/626890933111 for better results. Can you find additional factors?

To be clear, the number (2^64000-1) was arbitrary and only used to make sure that it could find any factors at all. I'm also checking with a known 40-digit factor that should be found in Stage 2 (and is). I'll try out the number you suggested and see if anything turns up.

Edit: Also, why does it being a highly composite number make the results dubious? Still teaching myself the basics of ECM, so I don't know enough to know what I don't know.

The ECM code can recognize special input forms. For example, it is known that ecm switches to a special branch for factoring the 2^4096+1 c1133 cofactor, [U][I]even if[/I][/U] you give the decimal representation on input. Try it (and use -v switch, to see what is going on in detail).

If it can do that, it can (I don't know if it does in this version, but it might in the future version) recognize algebraic factorizations and run itself on cofactors which are at least twice smaller. So, you will be getting timings that you'd expect to be [I]typical [/I]for the bit size of the input number but instead you will get timings for a much smaller number.

If you take a 2^prime-1 as an input, you will not depend on the implementation details.

[QUOTE=Batalov;379181].[/QUOTE]
:goodposting:

Follow-up question: If it can find the two known factors (apart from any larger ones it may find) of 2^63997-1, would you have confidence in it working properly?

Using non-base 2 numbers (like [URL="http://factordb.com/index.php?id=1100000000535556578"]this one[/URL]) suggests that there's something strange going on. My results are very hit-or-miss.

To clarify a bit more: if I put in (5^480*12-1) and use B1=100000 with 480 curves (the default number of curves), I find the factor 11 in stage 1 and factors 97369 and 94165528343 in Stage 2. My concern is that I don't seem to find relatively small factors sometimes, even when I run enough curves to have the equivalent of multiple tXX. If anybody finds a large factor (25-35 digits?) with a known sigma from a composite larger than 2^1018-1, please let me know.