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Old 2012-04-13, 13:16   #1
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Default TF times

Hi,

Why is it that TF M805085069 from 65 to 66 bits takes 4 minutes but TF M101108803 from 65 to 66 bits takes half an hour on the same CPU?
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Old 2012-04-13, 14:06   #2
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As a number gets larger there are fewer possible factors to test in a range.

A potential factor has the form 2*p*k+1.

This means when comparing p=805085069 and p=101108803 you would expect that there are approx 7.9 times (805085069/101108803) more factors to test in the 100M number vs the 800M number. This means the time would be approx 7.9 times longer.

4 minutes * 7.9 is approx 31 minutes

Grant.
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Old 2012-04-13, 14:06   #3
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Quote:
Originally Posted by Unregistered View Post
Hi,

Why is it that TF M805085069 from 65 to 66 bits takes 4 minutes but TF M101108803 from 65 to 66 bits takes half an hour on the same CPU?
It sounds like there is a process running in the background causing a slowdown during your testing, as the time to run a 100M exp to a given bit level will always take less time than 80M exponent.
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Old 2012-04-13, 14:13   #4
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Thanks a lot gjmccrac, this explains it.
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Old 2012-04-13, 14:53   #5
petrw1
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Quote:
Originally Posted by bcp19 View Post
It sounds like there is a process running in the background causing a slowdown during your testing, as the time to run a 100M exp to a given bit level will always take less time than 80M exponent.
800M
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Old 2012-04-13, 19:23   #6
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Quote:
Originally Posted by gjmccrac View Post
As a number gets larger there are fewer possible factors to test in a range.

A potential factor has the form 2*p*k+1.

This means when comparing p=805085069 and p=101108803 you would expect that there are approx 7.9 times (805085069/101108803) more factors to test in the 100M number vs the 800M number. This means the time would be approx 7.9 times longer.

4 minutes * 7.9 is approx 31 minutes

Grant.
interesting that means the first one doable in under a second for that bit range should be around 192B
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Old 2012-04-13, 19:40   #7
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Quote:
Originally Posted by petrw1 View Post
800M
I should have seen that :/ Sometimes the eyes just don't work right.
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Old 2012-04-14, 11:45   #8
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It's hard to read these; it would help to put commas in.

M805,085,069
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