Welcome! First edit doecm.ini to use your name instead of mine when submitting factors, and decide whether you want to use autosubmit. There are also some other settings you may want to look at. Make sure the names of your gmp-ecm and wget programs are correct for example. If you're using windows then those programs are included in this archive so the settings should be alright already. Then execute # run to start. This script sets the process priority to idle and starts doecm. The run script can take arguments as well (though run.bat is limited to 9 arguments), which are then passed to doecm and overrides the settings in doecm.ini. An example to clear out confusion: # run -b1 11000000 -nmin 651 overrides the b1 and nmin settings in doecm.ini and runs B1=11M curves on numbers with n >= 651. If you're going to be running several instances of the program (on multi-cpu systems), be sure to use a separate directory for each. By default doecm does recommended work -- it tries to factor the numbers that the server feels are most needed using the settings deemed most appropriate. At the time of writing this corresponds to fetching all composites for k*2^n+-1, k=3,5,7,9,11 1<=n<=1000 from the server and running 1 ecm curve with B1=1M on each, and then raising B1 by 1000, fetching an updated list and starting over again. The sigma values used to find primes are saved in doecm_sigmas.txt should you need them. All found factors are also written to doecm_factors.txt (appended to the end). You will need Paul Zimmermann's gmp-ecm to use this program at all, and a wget no older than v1.9 if you plan on using the autosubmit feature. Downloading composites in compressed format requires gzip. All these programs are included in the windows version of this archive. If you're always connected to the internet I highly recommend you use the auto features. Then you basically won't have to do anything once you've started the program. Except go to the website and marvel at your factors in the log, that is. ----- For windows only: Included in this zip are executable versions of wget v1.9.1 from http://studwww.ugent.be/~bpuype/wget/ gmp-ecm v5.0.3 from http://www.geocities.com/greatpsycho/ and gzip v.1.2.4 from http://www.gzip.org/ If you have a processor with SSE2 instructions you may want to download a P4 flavor of gmp-ecm. One quirk of the "start" program used to set priority in run.bat is that it disables ctrl-c. Ctrl-break still works though. ----- For Linux only: Pressing ctrl-c will only kill the currently running ecm, not the doecm that started it. As a result you may want to use "killall doecm" to actually kill the program. When you do that the currently running ecm runs to completion and doecm won't be able to handle the potential factor it finds. You can look in doecm_ecm_result to see if that last ecm found anything. If you're using debian you can run # apt-get install gmp-ecm to install gmp-ecm and everything it needs. It's in the "testing/unstable" apt category though, so you'll need to make sure you can access those. Otherwise you can get the .deb manually at http://packages.debian.org/unstable/math/gmp-ecm.html If you're using gentoo you can run # emerge gmp to install GMP (a requirement for gmp-ecm). You'll still have to compile gmp-ecm though. Other systems may need to compile both GMP and gmp-ecm. Or perhaps you can install the .deb file? (see above) Again, please make sure you have a wget no older than v1.9 if you want to use the autosubmit feature. ----- Compiling doecm.cc: You will need a relatively fresh g++ if you want to do this. v3.3 works nicely. Then simply run # g++ -O2 doecm.cc -o doecm and you'll have a working doecm in no time. ----- Links: You can download the used programs and their source code at: GMP: http://www.swox.se/gmp/ gmp-ecm: http://www.loria.fr/~zimmerma/records/ecmnet.html wget: http://www.gnu.org/software/wget/wget.html Best of luck, Mikael Klasson factors T mklasson.com http://mklasson.com/factors/