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[#21373] replace estimate_lognorm() in las -dup

Date:
2017-06-13 11:57
Priority:
3
State:
Open
Submitted by:
Paul Zimmermann (zimmerma)
Assigned to:
Nobody (None)
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Summary:
replace estimate_lognorm() in las -dup

Detailed description
with the -dup option of las, we use a function (estimate_lognorm), to identify potential duplicates corresponding to another special-q, that might give different initial lognorms than when doing the real sieving.

As a consequence, if estimate_lognorm gives a value larger than las, after removing factor base primes we might fall outside mfb, and thus declare the relation as not duplicate whereas it is a dup.

If/when we have a function that gives exactly the same initial lognorm as las (even if not 100% accurate) we should call it instead of estimate_lognorm.
Message  ↓
Date: 2017-06-13 20:26
Sender: Emmanuel Thomé

looking a very tiny bit into it, it seems that las-duplicate.cpp does reinitialize the sieve_info structure based on the special-q, and that includes the lognorms structures as well (via si.update_norm_data()). So chances are that L.lognorm(i,j) is close to what you want.

For the record, L.fiil(unsigned char * S, int N) fills the bucket region of index N at position S with the lognorms. This one is really identical to what we use in sieving. This being said, the new lognorm code is more accurate than the previous one, so I don't think there's a compelling need for that level of accuracy.

Date: 2017-06-13 20:22
Sender: Emmanuel Thomé

I've just merged my refresh of the lognorms code.

las-duplicate.cpp now uses L.lognorm(i,j) to compute a lognorm in the (i,j) plane, based on a lognorm structure which is initialized previously.

I think that this is all functionally equivalent to the previous state, so I doubt you'll get immediately what you want here.

On the other hand, it's pretty likely now that the desired functionality can be obtained with little effort.

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