The other thing that you have to be aware of is that 8^n is not 8 multiplied by itself n times. You are probably using logs to compute this. Here is a sample of 8^(1:20). The value of 8^2 is 64.000000000000004 (not exactly an integer); roundoff errors are apparent in the other values.
> 8^(1:20) [1] 8.0000000000000000e+00 6.4000000000000004e+01 5.1200000000000001e+02 4.0960000000000001e+03 [5] 3.2768000000000002e+04 2.6214400000000002e+05 2.0971519999999999e+06 1.6777215999999999e+07 [9] 1.3421772800000000e+08 1.0737418240000001e+09 8.5899345920000005e+09 6.8719476736000003e+10 [13] 5.4975581388799997e+11 4.3980465111039999e+12 3.5184372088832001e+13 2.8147497671065600e+14 [17] 2.2517998136852482e+15 1.8014398509481984e+16 1.4411518807585588e+17 1.1529215046068471e+18 > On 1/30/06, Ionut Florescu <[EMAIL PROTECTED]> wrote: > > I am a statistician and I come up to an interesting problem in > cryptography. I would like to use R since there are some statistical > procedures that I need to use. > However, I run into a problem when using the modulus operator %%. > > I am using R 2.2.1 and when I calculate modulus for large numbers (that > I need with my problem) R gives me warnings. For instance if one does: > a=1:40; > 8^a %% 41 > one obtains zeros which is not possible since 8 to any power is not a > multiple of 41. > In addition when working with numbers larger that this and with the mod > operator R crashes randomly. > > I believe this is because R stores large integers as real numbers thus > there may be lack of accuracy when applying the modulus operator and > converting back to integers. > > So my question is this: Is it possible to increase the size of memory > used for storing integers? Say from 32 bits to 512 bits (Typical size of > integers in cryptography). > > Thank you, any help would be greatly appreciated. > Ionut Florescu > > ______________________________________________ > R-help@stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html > -- Jim Holtman Cincinnati, OH +1 513 247 0281 What the problem you are trying to solve? [[alternative HTML version deleted]] ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
