[GAP Forum] GAP

[Max Horn]

> Am 16.04.2015 um 20:24 schrieb Bill Allombert <Bill.Allombert at math.u-bordeaux.fr>:
> 
>> On Thu, Apr 16, 2015 at 05:35:20PM +0100, Sandeep Murthy wrote:
>> 
>> Once you’ve defined the variables a and p you can just do
>> 
>>    gap> a^p mod p = a mod p;
>> 
>> and
>> 
>>   gap> a^(p-1) mod p = 1;
> 
> I would suggest instead to do something like 
> ZmodnZObj(a,p)^(p-1);
> instead to avoid computing a^(p-1) as a large integer.
> 
> gap> ZmodnZObj(2,4294967297)^4294967296;
> ZmodnZObj( 1, 4294967297 )
> gap> time;
> 0
> gap> 2^4294967296 mod 4294967297;
> 1
> gap> time;
> 2965

Or use PowerMod resp. PowerModInt.


> 
> Cheers,
> Bill.
> 
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