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Conference rusure::math

Title:Mathematics at DEC
Moderator:RUSURE::EDP
Created:Mon Feb 03 1986
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:2083
Total number of notes:14613

546.0. "?? Division/factoring algorithms ??" by SHEILA::PUCKETT (Very Asian Gold Box) Wed Jul 30 1986 00:29

    Has anyone got network-readable descriptions, or book references,
    to algorithms for:
    
    1) fast multiprecision integer operations (esp. division)
    
    2) factoring (pollard rho, quadratic sieve etc.)

    Any light shed on these would be appreciated.
    
    - Giles
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546.1ENGINE::ROTHWed Jul 30 1986 12:248
    A recent book published by Birkhauser by Hans Riesel on prime numbers
    may be what you are looking for.  I don't have a copy in my office, but
    you could call Birkhauser in Boston about the book; it includes many
    routines in PASCAL.

    Of course, Knuth has lots of info too.

    - Jim
546.2'Scientific Pascal'EAGLE7::BESTR. D. Best, 32 bit sys. arch. & A.D., VAXBIWed Aug 06 1986 21:3224
< Note 546.0 by SHEILA::PUCKETT "Very Asian Gold Box" >
                    -< ?? Division/factoring algorithms ?? >-

    Has anyone got network-readable descriptions, or book references,
    to algorithms for:
    
    1) fast multiprecision integer operations (esp. division)
    
    2) factoring (pollard rho, quadratic sieve etc.)

    Any light shed on these would be appreciated.
    
    - Giles

>	A book reference with Pascal sources:
>	( but I can't say how fast they are )

>	re: multiprecision integer ops (I'm not sure about division)

>	'Scientific Pascal' by Harley Flanders, Reston Publishing Co.

>	Available in the DEC library.

>		/R Best
546.3Maybe it can be dug out of the libraryMODEL::YARBROUGHTue Sep 30 1986 17:503
The Pollard Rho algorithm is used in MAPLE for factoring large integers.
The MAPLE manual only describes it by name, though. A simpler algorithm
(which fails for large factors) is also available. 
546.4PollardTAV02::NITSANNitsan Duvdevani, Digital IsraelThu Oct 09 1986 12:0113
 -- About the Pollard algorithm, if I remember correctly, it goes
    something like this:

Statisticly, when you have a set of k items, it takes about sqrt(k) random
choices to repeat the same choice with high probability. Assuming you have
a number n = p*q, then it takes about sqrt(p) random choices to get two
values with the same residue mod p. So choose random pairs and test the
gcd between their difference and n.

This is just the basic idea. The algorithm itself has more points of
optimization etc.

Nitsan