This is from http://trac.sagemath.org/15517, ecm doesn't find a factor. But there is one with 17 digits, so should be just fine? Does anybody have a suggestion on what to do if ecm quits without finding a factor? When is it safe enough to assume that there is no factor?
GMP-ECM 6.4.4 [configured with MPIR 2.6.0, --enable-asm-redc] [ECM] Input number is 602400691612422154516282778947806249229526581 (45 digits) Using B1=2000, B2=147396, polynomial x^1, sigma=4179203867 Step 1 took 2ms Step 2 took 3ms Run 2 out of 1000000000: Using B1=2399, B2=2399-186156, polynomial x^1, sigma=4164584203 Step 1 took 2ms Step 2 took 4ms Run 3 out of 1000000000: Using B1=2806, B2=2806-224406, polynomial x^1, sigma=3854196504 Step 1 took 3ms Step 2 took 3ms Run 4 out of 1000000000: Using B1=3221, B2=3221-294786, polynomial x^1, sigma=3420982637 Step 1 took 3ms Step 2 took 5ms Run 5 out of 1000000000: Using B1=3644, B2=3644-294786, polynomial x^1, sigma=1430191020 [...] Using B1=22052, B2=22052-5026572, polynomial x^1, sigma=1562069045 Step 1 took 20ms Step 2 took 26ms Run 38 out of 1000000000: Using B1=22779, B2=22779-5026572, polynomial x^1, sigma=1306733316 Step 1 took 21ms Step 2 took 25ms Run 39 out of 1000000000: Using B1=23516, B2=23516-5031192, polynomial x^1, sigma=2409042976 Step 1 took 22ms Step 2 took 25ms Run 40 out of 1000000000: Using B1=24263, B2=24263-5031192, polynomial x^1, sigma=518178309 Step 1 took 22ms Step 2 took 26ms ********** Factor found in step 2: 602400691612422154516282778947806249229526581 Found input number N -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at http://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/groups/opt_out.
