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MathGroup Archive 2008

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Re: QuickFactorInteger


Artur wrote:
> Dear Mathematica Gurus,
> 
> Who know how construct procedure to obtained reasonable primes divisors 
> of big number in reasonable time. If number have two big primes divisors 
> range 40 decimal digits Mathematica function FactorInteger working hours 
> and do nothing. I want do time limit (e.g. 5 second) and received list 
> of factors which was obtained after these 5 seconds or do other  trick 
> to obtained partialy result of FactorInteger.
> 
> Best wishes
> Artur

Give a second argument of Automatic. This is similar to the 
pre-version-6 option FactorComplete->False.

Example:

In[10]:= p1 = NextPrime[10^40];

In[11]:= p2 = NextPrime[10^42];

In[12]:= p3 = Prime[2222];

In[13]:= p4 = Prime[5555555];

In[14]:= Timing[fax = FactorInteger[7*127*p1*p2*p3*p4, Automatic]]

Out[14]= {16.4915, {{7, 1}, {127, 1}, {19583, 1}, {96210113, 1}, 
{1000000000000000000000000000000000000012163000000000000000000000000000\
         0000000007623, 1}}}

Daniel Lichtblau
Wolfram Research


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