murdoch@stats.uwo.ca
2006-Jan-30 18:50 UTC
[Rd] [R] Integer bit size and the modulus operator (PR#8541)
On 1/30/2006 1:39 PM, Ionut Florescu wrote:> Thank you for the quick reply, I will look into the R packages. > For crashing R try this: > > generator.zp=function(x,p) > {a=1:(p-1); b=x^a%%p; > if(all(b[1:(p-2)]!=1)&&(b[p-1]==1)){return(x, " Good ")} > else{return(x, " No Good, try another integer ")} > }Thanks, I can reproduce the crash using for (x in 10:100) generator.zp(x, 41) I'll see if I can track down what's going wrong. By the way, you're not supposed to use two arguments to return(): that's not supposed to be allowed any more. I'm somewhat surprised you don't get an error from it. But that's not the cause of the crash. Duncan Murdoch> > This checks if element x is a generator of the group Z_p. If you try > this function for p = 41 and x various increasing values eventually it > will crash R. That is what I meant by random, at first I started x=2,3 > so on, when I got to 8, R crashed. Now apparently I can get to 15. When > I tried again I got to 20. > > Ionut Florescu > > > Duncan Murdoch wrote: >> On 1/30/2006 11:32 AM, Ionut Florescu 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. >> >> Could you keep a record of the random crashes, and see if you can make >> any of them repeatable? R shouldn't crash. If you can find a >> repeatable way to make it crash, then that's a bug that needs to be >> fixed. (If it crashes at random it should still be fixed, but it's so >> much harder to fix that it's unlikely to happen unless the cases are >> ones that look likely to come up in normal situations.) >> >> >>> >>> 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). >> >> No, but there is at least one contributed package that does multiple >> precision integer arithmetic. I can't remember the name of it right >> now, but Google should be able to find it for you... >> >> Duncan Murdoch >>> >>> Thank you, any help would be greatly appreciated. >>> Ionut Florescu >>> >>> ______________________________________________ >>> R-help at 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 >> >>
ripley@stats.ox.ac.uk
2006-Jan-30 19:26 UTC
[Rd] [R] Integer bit size and the modulus operator (PR#8541)
On Mon, 30 Jan 2006 murdoch at stats.uwo.ca wrote:> On 1/30/2006 1:39 PM, Ionut Florescu wrote: >> Thank you for the quick reply, I will look into the R packages. >> For crashing R try this: >> >> generator.zp=function(x,p) >> {a=1:(p-1); b=x^a%%p; >> if(all(b[1:(p-2)]!=1)&&(b[p-1]==1)){return(x, " Good ")} >> else{return(x, " No Good, try another integer ")} >> } > > Thanks, I can reproduce the crash using > > for (x in 10:100) generator.zp(x, 41) > > I'll see if I can track down what's going wrong. By the way, you're not > supposed to use two arguments to return(): that's not supposed to be > allowed any more. I'm somewhat surprised you don't get an error from > it. But that's not the cause of the crash.You do get a warning, though. It *is* allowed, see ?return. One error is the following in real_binary: if (n1 > n2) copyMostAttrib(s1, ans); else if (n1 == n2) { copyMostAttrib(s2, ans); copyMostAttrib(s1, ans); } else copyMostAttrib(s2, ans); Here ans is not PROTECTED. The second is in the warning, which causes allocation when ans is not protected. Fixed in R-devel and 2.2.1 patched.> Duncan Murdoch > > >> >> This checks if element x is a generator of the group Z_p. If you try >> this function for p = 41 and x various increasing values eventually it >> will crash R. That is what I meant by random, at first I started x=2,3 >> so on, when I got to 8, R crashed. Now apparently I can get to 15. When >> I tried again I got to 20. >> >> Ionut Florescu >> >> >> Duncan Murdoch wrote: >>> On 1/30/2006 11:32 AM, Ionut Florescu 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. >>> >>> Could you keep a record of the random crashes, and see if you can make >>> any of them repeatable? R shouldn't crash. If you can find a >>> repeatable way to make it crash, then that's a bug that needs to be >>> fixed. (If it crashes at random it should still be fixed, but it's so >>> much harder to fix that it's unlikely to happen unless the cases are >>> ones that look likely to come up in normal situations.) >>> >>> >>>> >>>> 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). >>> >>> No, but there is at least one contributed package that does multiple >>> precision integer arithmetic. I can't remember the name of it right >>> now, but Google should be able to find it for you... >>> >>> Duncan Murdoch >>>> >>>> Thank you, any help would be greatly appreciated. >>>> Ionut Florescu >>>> >>>> ______________________________________________ >>>> R-help at 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-devel at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > >-- Brian D. Ripley, ripley at stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595
ripley@stats.ox.ac.uk
2006-Jan-30 19:40 UTC
[Rd] [R] Integer bit size and the modulus operator (PR#8541)
On Mon, 30 Jan 2006, Prof Brian Ripley wrote:> On Mon, 30 Jan 2006 murdoch at stats.uwo.ca wrote: > >> On 1/30/2006 1:39 PM, Ionut Florescu wrote: >>> Thank you for the quick reply, I will look into the R packages. >>> For crashing R try this: >>> >>> generator.zp=function(x,p) >>> {a=1:(p-1); b=x^a%%p; >>> if(all(b[1:(p-2)]!=1)&&(b[p-1]==1)){return(x, " Good ")} >>> else{return(x, " No Good, try another integer ")} >>> } >> >> Thanks, I can reproduce the crash using >> >> for (x in 10:100) generator.zp(x, 41) >> >> I'll see if I can track down what's going wrong. By the way, you're not >> supposed to use two arguments to return(): that's not supposed to be >> allowed any more. I'm somewhat surprised you don't get an error from >> it. But that's not the cause of the crash. > > You do get a warning, though. It *is* allowed, see ?return. > > One error is the following in real_binary: > > if (n1 > n2) > copyMostAttrib(s1, ans); > else if (n1 == n2) { > copyMostAttrib(s2, ans); > copyMostAttrib(s1, ans); > } > else > copyMostAttrib(s2, ans); > > Here ans is not PROTECTED.I think this one was a consequence of the other one. I did get a valgrind error from there, but it looks as if copyMostAttrib does the necessary protection, if ans has not already been damaged.> The second is in the warning, which causes allocation when ans is not > protected. > > Fixed in R-devel and 2.2.1 patched. > > >> Duncan Murdoch >> >> >>> >>> This checks if element x is a generator of the group Z_p. If you try >>> this function for p = 41 and x various increasing values eventually it >>> will crash R. That is what I meant by random, at first I started x=2,3 >>> so on, when I got to 8, R crashed. Now apparently I can get to 15. When >>> I tried again I got to 20. >>> >>> Ionut Florescu >>> >>> >>> Duncan Murdoch wrote: >>>> On 1/30/2006 11:32 AM, Ionut Florescu 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. >>>> >>>> Could you keep a record of the random crashes, and see if you can make >>>> any of them repeatable? R shouldn't crash. If you can find a >>>> repeatable way to make it crash, then that's a bug that needs to be >>>> fixed. (If it crashes at random it should still be fixed, but it's so >>>> much harder to fix that it's unlikely to happen unless the cases are >>>> ones that look likely to come up in normal situations.) >>>> >>>> >>>>> >>>>> 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). >>>> >>>> No, but there is at least one contributed package that does multiple >>>> precision integer arithmetic. I can't remember the name of it right >>>> now, but Google should be able to find it for you... >>>> >>>> Duncan Murdoch >>>>> >>>>> Thank you, any help would be greatly appreciated. >>>>> Ionut Florescu >>>>> >>>>> ______________________________________________ >>>>> R-help at 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-devel at r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-devel >> >> > > -- > Brian D. Ripley, ripley at stats.ox.ac.uk > Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ > University of Oxford, Tel: +44 1865 272861 (self) > 1 South Parks Road, +44 1865 272866 (PA) > Oxford OX1 3TG, UK Fax: +44 1865 272595 >-- Brian D. Ripley, ripley at stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595