AdvancedFactor

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AdvancedFactor is one of the undocumented options for Prime95, which was removed in later versions. The format for the line you add to the worktodo.ini file is:

AdvancedFactor=start_exponent, end_exponent, b1, b2

where:

start_exponent is the first exponent in a range to test.
end_exponent is the last exponent in a range to test.
b1 is the starting bit-depth to test with.
b2 is the ending bit-depth to test with.

The line:

AdvancedFactor=1000000, 2000000, 64, 68

would attempt to trial-factor every prime exponent between 1,000,000 and 2,000,000 for factors between 264 and 268.

If you don't want to check a range of exponents, and instead just want to check a specific set of exponents, you need to use the line in worktodo.ini:

Factor=exp, bd

where:

exp is the exponent to trail-factor.
bd is where to begin trial-factoring at (2bd).

The line:

Factor=42099977, 61

would attempt to trial-factor the exponent 42,099,977 starting at 261 and continue until it either found a factor or reached 269 (Prime95's default breakpoint for this exponent), unless you used the FactorOverride line in prime.ini.

If you put say:

FactorOverride=66

in prime.ini, Prime95 would attempt to factor it only up to 266 instead of 269.

You would have to put a Factor= line in worktodo.ini for each and every exponent you wanted to test.

If you are using the most recent version of Prime95, v24.14, it will accept exponents to trial-factor up to 2 Billion. While none of the documentation says specifically, looking at the source code, it would appear that Prime95 can do SSE2 factoring up to 286 and non-SSE2 factoring up to 296.