From: Liaw, Andy <andy_liaw_at_merck.com>

Date: Tue 31 Jan 2006 - 05:39:07 EST

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 Received on Tue Jan 31 05:52:21 2006

Date: Tue 31 Jan 2006 - 05:39:07 EST

R is probably not the best tool for handling large integers...

AFAIK Python has the interesting feature of not only having a `long' integer type (that can store arbitrarily large integers), but can convert a regular 4-byte int to the `long' type when necessary. Perhaps that would be a better tool for the purpose.

Andy

From: jim holtman

*>
*

> You have reached the maximum value that can be stored accurately in a

*> floating point number. That is what the error message is
**> telling you. I
**> get 21 warnings and this says that at 8^20 I am now
**> truncating digits in the
**> variable. You only have about 54 bits in the floating point
**> number and you
**> exceed this about 8^19.
**>
**> > a=1:40;
**> > 8^a %% 41
**> [1] 8 23 20 37 9 31 2 16 5 40 33 18 21 4 32 10 39 25 36
**> 1 8 23 20
**> 37 9 31 2 16 5 40 33
**> [32] 18 21 4 32 10 0 0 0 0
**> There were 21 warnings (use warnings() to see them)
**> > warnings()
**> Warning messages:
**> 1: probable complete loss of accuracy in modulus
**> 2: probable complete loss of accuracy in modulus
**> 3: probable complete loss of accuracy in modulus
**> 4: probable complete loss of accuracy in modulus
**> 5: probable complete loss of accuracy in modulus
**> 6: probable complete loss of accuracy in modulus
**> 7: probable complete loss of accuracy in modulus
**> 8: probable complete loss of accuracy in modulus
**> 9: probable complete loss of accuracy in modulus
**> 10: probable complete loss of accuracy in modulus
**> 11: probable complete loss of accuracy in modulus
**> 12: probable complete loss of accuracy in modulus
**> 13: probable complete loss of accuracy in modulus
**> 14: probable complete loss of accuracy in modulus
**> 15: probable complete loss of accuracy in modulus
**> 16: probable complete loss of accuracy in modulus
**> 17: probable complete loss of accuracy in modulus
**> 18: probable complete loss of accuracy in modulus
**> 19: probable complete loss of accuracy in modulus
**> 20: probable complete loss of accuracy in modulus
**> 21: probable complete loss of accuracy in modulus
**> >
**> > 8^35
**> [1] 4.056482e+31
**> > 8^36
**> [1] 3.245186e+32
**> > 8^19
**> [1] 1.441152e+17
**> > 8^19%%41
**> [1] 36
**> > 8^20
**> [1] 1.152922e+18
**> > 8^20%%41
**> [1] 1
**> Warning message:
**> probable complete loss of accuracy in modulus
**> >
**>
**>
**>
**> On 1/30/06, Ionut Florescu <ifloresc@stevens.edu> 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
**>
*

>

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 Received on Tue Jan 31 05:52:21 2006

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