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• ... What do you mean by backtracking here? Is it that if you try to factor n+1 or n-1 in a proof and get to a large factor, you try to prove it prime in order
Message 1 of 7 , Nov 8, 2001
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At 02:43 AM 11/9/2001 +0100, Marcel Martin wrote:

>Well, since I still don't know whether I will add a backtracking
>feature or not to the next Primo release, if ever you have something

What do you mean by backtracking here? Is it that if you try to factor n+1
or n-1 in a proof and get to a large factor, you try to prove it prime in
order to make the n+1 or n-1 proof of the original number work?

+--------------------------------------------------------+
| Jud McCranie |
| |
| 137*2^261147+1 is prime! (78,616 digits, 5/2/00) |
+--------------------------------------------------------+
• Marcel Martin (famously fast worker famously slow decider:-) ... begin{special_pleading} I say this: Pease retain the bactracking of Primo 1.1.0 as an
Message 2 of 7 , Nov 8, 2001
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Marcel Martin
(famously fast worker
famously slow decider:-)
wrote:

> Well, since I still don't know whether I will add a
> backtracking feature or not to the next Primo release,
> if ever you have something to say about it, please, say it now.

I say this: Pease retain the bactracking of Primo 1.1.0
as an *option*. The likes of Giovanni, Hans, Greg, Nathan,
Bouk and I are wise enough to experiment as to
when to use it. It would be a great shame to throw away
one of your many achievements in implementing it.

David
• ... OK. Knuth uses the term backtrack in the example in section 4.5.4. +---------------------------------------------------------+ ...
Message 3 of 7 , Nov 9, 2001
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At 06:45 AM 11/9/2001 +0100, Marcel Martin wrote:

>No. In that case I would surely have told of 'recursivity' :-)

OK. Knuth uses the term "backtrack" in the example in section 4.5.4.

+---------------------------------------------------------+
| Jud McCranie |
| |
| Programming Achieved with Structure, Clarity, And Logic |
+---------------------------------------------------------+
• Hello! ... David is right. I d also add that it would be nice to take into account the number of bits gained in previous tests when backtracking. Best wishes,
Message 4 of 7 , Nov 9, 2001
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Hello!

Marcel Martin wrote:

> Well, since I still don't know whether I will add a backtracking
> feature or not to the next Primo release, if ever you have something

> I say this: Pease retain the bactracking of Primo 1.1.0
> as an *option*.

David is right. I'd also add that it would be nice to take into account the
number of bits gained in previous tests when backtracking.

Best wishes,

Andrey
• ... I think that *both* backtracking AND more factorization power is most useful when you are tackling numbers beyond a certain (let s say 3k+) size. Hans
Message 5 of 7 , Dec 1, 2001
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Marcel Martin wrote:

> Well, since I still don't know whether I will add a backtracking
> feature or not to the next Primo release, if ever you have something

I think that *both* backtracking AND more factorization power is most
useful when you are tackling numbers beyond a certain (let's say 3k+)
size.

Hans
• Marcel Martin wrote ... I didn t dare tell you that I use it all the time, including the advanced set up. I thought you might foam at the mouth :-) if I showed
Message 6 of 7 , Dec 2, 2001
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Marcel Martin wrote

> There were very few answers to my post.

I didn't dare tell you that I use it all the time,

I thought you might foam at the mouth :-)
if I showed you:

Binary size = 7560
Running time 53h 38mn 42s for path
Running time 11h 0mn 50s for rest
with backtrack at end of Run 1 Part 2
at 1 GHz

Thanks for letting me be so "inefficient" :-)

David
• PS: I looked to see how many backtracks there were in ... answer = 15 backtracks in 353 steps For my money, that was a small price to pay, at this bitsize, for
Message 7 of 7 , Dec 2, 2001
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PS: I looked to see how many backtracks there were in

> Binary size = 7560
> Running time 53h 38mn 42s for path

answer = 15 backtracks in 353 steps

For my money, that was a small price to pay,
at this bitsize, for complete avoidance of Run 2.
Opinions may vary, but experiment should
at least be allowed, please, Marcel.

David
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