unsigned long long int

Question

I was submitting a matrix exponentiation code in C language for finding the nth fibonacci and I was using long long int variable for storing the answer modulo 10000007 of nth fibonacci, and the judge was giving "time limit exceeded" but when I used "unsigned long long int" my code was accepted within the time and the execution time was reduced.

I was unable to understand why long long int was giving "time limit exceeded" and "unsigned long long int" was accepted? (Answers for extreme test cases were coming correct in both cases)

And you have total confidence that the architecture on the judge's machine is the same as yours? — Chris Eberle, Feb 18 '12 at 05:16
http://stackoverflow.com/questions/4712315/performance-of-unsigned-vs-signed-integers — Mitch Wheat, Feb 18 '12 at 05:18
I am not sure about the architecture of the judge but main motive was to to understand why unsigned long long int was working fast. — L.ppt, Feb 18 '12 at 05:25

score 5 · Accepted Answer · edited May 23 '17 at 11:48

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In order not to replicate anybody's effort, please see this question and this more advanced question and answers of the same topic. dthorpe's answer in this one is highly detailed as well. wheaties' first comment here is worth checking as a first trial.

edited May 23 '17 at 11:48

Community

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answered Feb 18 '12 at 06:17

OmarOthman

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there is overhead when we use unsigned when mixed with doubles, but my code deals with the multiplication and "unsigned int" is working faster than the "int" and yes now i can also check for multiplication by comparing the assembly code for both kind of multiplications...:) – L.ppt Feb 18 '12 at 09:28

unsigned long long int

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