Quote:
Originally Posted by nivek000
Does the performance of SNFS vary wildly? I saw a C155 number (a factor of a larger C205 number) factor with SNFS in a little over 2 hours. Now I have a C160 running (a factor of a larger C213 number) that is estimated to run like 35 hours. The stated scaled difficulty is definitely different (167 for the former vs 218 for the latter). I am just surprised that there can be such a longer runtime for just 5 additional digits. Is this an effect of polynomial selection? Is it possible YAFU (version 2.07) made a poor choice for the latter number, or is this par for the course with SNFS?
Thanks!
 Kevin

Is the C160 a quartic, by chance? The degree of the polynomial matters and degree 4 for a C213 is suboptimal. Unfortunately this is the only way to make a SNFS poly, sometimes. It's better than running GNFS (although this isn't always true!).
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If you like, post the target number and what yafu picked and we can help figure out if it was the best choice.