This fix also fixed a segfault Fredrik found coincidentally at the same time.
Can we do a quick 2.1.1 release for this? I think nothing more is required than to do a version change, tarball and upload to the website. It passes make check on my machine with this patch, and given that it is pure C and fixed the problem, and a well understood patch, I think a fairly good candidate for a quick release. Bill. On 4 September 2010 17:29, Jason <[email protected]> wrote: > Commited to mpir-2.1 and trunk . I should add a test case , was it when dn==nn > , although I couldn't get the K8 to fail. > > Jason > > > On Saturday 04 September 2010 16:47:21 Bill Hart wrote: >> OK, I think the following patch to mpn/generic/divexact.c fixes this issue: >> >> wbh...@selmer:~/mpir-2.1.1/mpn/generic$ diff divexact.c divexact.old >> 131,141c131,138 >> < if (qn) >> < { >> < inv = TMP_ALLOC_LIMBS(dn); >> < mpn_invert(inv, dp, dn); >> < cy = mpn_inv_divappr_q(qp, n2p, nn, dp, dn, inv); >> < if (!extend) qp[qn] = cy; >> < >> < if ((qp[0] & 1) + q_even != 1) /* quotient is out by 1 */ >> < mpn_sub_1(qp, qp, qn + 1, 1); >> < } else >> < qp[0] = 1; // as dp is normalised, exact division means qp = 1 >> --- >> >> > inv = TMP_ALLOC_LIMBS(dn); >> > mpn_invert(inv, dp, dn); >> > cy = mpn_inv_divappr_q(qp, n2p, nn, dp, dn, inv); >> > if (!extend) qp[qn] = cy; >> > >> > if ((qp[0] & 1) + q_even != 1) /* quotient is out by 1 */ >> > >> > mpn_sub_1(qp, qp, qn + 1, 1); >> >> I don't seem to have an mpir svn setup at the moment. If someone could >> commit this and test, I'd be grateful. >> >> I don't see a reason to change the requirement that nn > dn, just that >> this requirement is respected by divexact, which it wasn't doing. >> >> Bill. >> >> On 4 September 2010 13:53, Bill Hart <[email protected]> wrote: >> > Ah, thanks for making progress with it. I'll see if I can chase it >> > through given what you've found. >> > >> > Bill. >> > >> > On 4 September 2010 13:43, Jason <[email protected]> wrote: >> >> On Saturday 04 September 2010 12:54:33 Jason wrote: >> >>> I can reproduce this error on boxen , which has gcc-4.2.4 >> >>> >> >>> ./configure --enable-assert --build=core2-unknown-linux-gnu >> >>> >> >>> and just run the test case to get an assertion failure , therefore this >> >>> looks like a real error , although I could not the failure when I >> >>> copied the core param into the K8 directory and changed cflags , so I >> >>> think this also depends on which HAVE_NATIVE functions are availible >> >> >> >> No , if I put the core2 params in the k8 directory and build on a k8 , I >> >> get the error(must of done something daft before). >> >> The error happens when mpn_divexact (which can accept denom limbs dn <= >> >> numer limbs nn) calls mpn_inv_divapprox_q (which requires just <) . >> >> With the k8 thresholds it reduces that case properly , but with core2 >> >> params it does not. It's possible that the k8 params could also produce >> >> this error as it just have to find the right input size. >> >> Unfortunately I'm not at all familiar with the code , I only roughly >> >> know the algorithm. >> >> >> >>> On Saturday 04 September 2010 11:36:35 Jason wrote: >> >>> > On Saturday 04 September 2010 11:09:23 Jason wrote: >> >>> > > The problem is that the gmp-mparam.h for core2 and nehalem have >> >>> > > some bad values in , when I replaced it with the k8 version it >> >>> > > was OK. I have to narrow down which values seem to be bad >> >>> > >> >>> > Actually thats not true , the values could be good , its just that it >> >>> > follows a different code path. Building with --enabel-assert we get >> >>> > this assertion failure when we run the code >> >>> > >> >>> > inv_divappr_q.c:46: GNU MP assertion failed: nn > dn >> >>> > Aborted >> >>> > >> >>> > > Jason >> >>> > > >> >>> > > On Saturday 04 September 2010 10:18:05 Jason wrote: >> >>> > > > Hi >> >>> > > > >> >>> > > > I can reproduce this error , I'm using gcc 4.4.4 , but only if I >> >>> > > > do a build for core2 or nehalem , the k8 build is OK , so >> >>> > > > perhaps it's the CFLAGS=- march=core2 that causes it? >> >>> > > > I'll change the flags and see if that makes a difference >> >>> > > > >> >>> > > > Jason >> >>> > > > >> >>> > > > On Friday 03 September 2010 23:49:14 Bill Hart wrote: >> >>> > > > > On 3 September 2010 23:44, Bill Hart >> >>> > > > > <[email protected]> >> >>> > >> >>> > wrote: >> >>> > > > > > Hi Jeroen, >> >>> > > > > > >> >>> > > > > > I've tried a variety of things to replicate this bug, >> >>> > > > > > including valgrinding with symbols on in MPIR and various >> >>> > > > > > compiler optimisation flags, but at least on my machine, I >> >>> > > > > > can't replicate it. >> >>> > > > > > >> >>> > > > > > If you have time, could you possibly help by taking the >> >>> > > > > > following steps: >> >>> > > > > > >> >>> > > > > > 1) Download a fresh copy of MPIR 2.1.1 from our website: >> >>> > > > > > http://www.mpir.org/ 2) Run ./configure; make; make check to >> >>> > > > > > verify that the library >> >>> > > > > > appears to compile OK on your machine (you could also try >> >>> > > > > > building your program against this clean library again if you >> >>> > > > > > haven't already done this) >> >>> > > > > > 3) Run ./configure again until about 30 lines are showing. >> >>> > > > > > You'll see something like >> >>> > > > > > >> >>> > > > > > CFLAGS="-O2 -m64 -march=k8 -mtune=k8" >> >>> > > > > > >> >>> > > > > > which will be indented (the string on your machine will be >> >>> > > > > > different). Copy the string that shows and alter the -O2 (or >> >>> > > > > > whatever you have) to -g, and pass to ./configure, e.g..: >> >>> > > > > > ./configure CFLAGS="-g -m64 -march=k8 -mtune=k8" >> >>> > > > > > 4) do >> >>> > > > > > make clean >> >>> > > > > > make >> >>> > > > > > 5) build your program against MPIR (to prevent it picking up >> >>> > > > > > a stray copy elsewhere, use -static when linking -- the >> >>> > > > > > library being in the .libs directory, the .h file in the top >> >>> > > > > > level directory of the MPIR source tree -- you'll have to >> >>> > > > > > set the -I and -L flags to gcc accordingly), e.g. I put the >> >>> > > > > > program in the top level mpir source directory and used: >> >>> > > > > > gcc -O2 mpirtest.c -o mpirtest -I. -L../.libs -lmpir -static >> >>> > > > > >> >>> > > > > Sorry, that should read: >> >>> > > > > >> >>> > > > > gcc -O2 mpirtest.c -o mpirtest -I. -L.libs -lmpir -static >> >>> > > > > >> >>> > > > > > 6) If you have valgrind installed on your machine, type: >> >>> > > > > > valgrind ./mpirtest >> >>> > > > > > and report to us the output. If not, a gdb backtrace, as you >> >>> > > > > > gave, may be sufficient. >> >>> > > > > > 7) If you have access to any other version of gcc on the same >> >>> > > > > > machine, it would also be useful to know if the same bug >> >>> > > > > > occurs with that version of gcc. >> >>> > > > > > >> >>> > > > > > This *may* be a compiler bug, but at this stage we have to >> >>> > > > > > assume it is more likely a bug in our code within MPIR. >> >>> > > > > > >> >>> > > > > > Bill. >> >>> > > > > > >> >>> > > > > > On 3 September 2010 22:10, Jeroen Demeyer >> >>> > > > > > <[email protected]> >> >>> > > >> >>> > > wrote: >> >>> > > > > >> Hello mpir-devel, >> >>> > > > > >> >> >>> > > > > >> I think I found a bug in MPIR 2.1.1 in mpz_divexact() (or >> >>> > > > > >> I'm doing something something very stupid). Running the >> >>> > > > > >> following program gives a Segmentation Fault: >> >>> > > > > >> >> >>> > > > > >> #include <mpir.h> >> >>> > > > > >> int main() >> >>> > > > > >> { >> >>> > > > > >> >> >>> > > > > >> mpz_t Z, R; >> >>> > > > > >> mpz_init(Z); >> >>> > > > > >> mpz_init(R); >> >>> > > > > >> mpz_ui_pow_ui(Z, 10, 100000); >> >>> > > > > >> mpz_divexact(R, Z, Z); >> >>> > > > > >> return 0; >> >>> > > > > >> >> >>> > > > > >> } >> >>> > > > > >> >> >>> > > > > >> >> >>> > > > > >> gdb backtrace: >> >>> > > > > >> >> >>> > > > > >> Program received signal SIGSEGV, Segmentation fault. >> >>> > > > > >> 0x00007fa2f2b5245d in mpn_submul_1 () from >> >>> > > > > >> /usr/local/src/pari/local/lib/libmpir.so.8 >> >>> > > > > >> (gdb) bt >> >>> > > > > >> #0 0x00007fa2f2b5245d in mpn_submul_1 () from >> >>> > > > > >> /usr/local/src/pari/local/lib/libmpir.so.8 >> >>> > > > > >> #1 0x00007fa2f2b73e72 in __gmpn_sb_divappr_q () from >> >>> > > > > >> /usr/local/src/pari/local/lib/libmpir.so.8 >> >>> > > > > >> #2 0x00007fa2f2b812f2 in __gmpn_inv_divappr_q () from >> >>> > > > > >> /usr/local/src/pari/local/lib/libmpir.so.8 >> >>> > > > > >> #3 0x00007fa2f2b88765 in __gmpn_divexact () from >> >>> > > > > >> /usr/local/src/pari/local/lib/libmpir.so.8 >> >>> > > > > >> #4 0x00007fa2f2b3fb4b in __gmpz_divexact () from >> >>> > > > > >> /usr/local/src/pari/local/lib/libmpir.so.8 >> >>> > > > > >> #5 0x0000000000400741 in main () at mpirtest.c:8 >> >>> > > > > >> >> >>> > > > > >> >> >>> > > > > >> My system is: >> >>> > > > > >> >> >>> > > > > >> $ uname -a >> >>> > > > > >> Linux arcanis 2.6.32-gentoo-r7 #5 SMP Thu Jun 10 23:07:26 >> >>> > > > > >> CEST 2010 x86_64 Intel(R) Core(TM)2 Duo CPU T5870 @ 2.00GHz >> >>> > > > > >> GenuineIntel GNU/Linux >> >>> > > > > >> >> >>> > > > > >> $ ./config.guess >> >>> > > > > >> core2-unknown-linux-gnu >> >>> > > > > >> >> >>> > > > > >> $ gcc --version >> >>> > > > > >> gcc-4.4.3 (Gentoo 4.4.3-r2 p1.2) 4.4.3 >> >>> > > > > >> >> >>> > > > > >> This is with MPIR 2.1.1 configured with ./configure >> >>> > > > > >> --enable-gmpcompat >> >>> > > > > >> >> >>> > > > > >> >> >>> > > > > >> This bug was found thanks to Sage (see >> >>> > > > > >> http://trac.sagemath.org/sage_trac/ticket/9837) >> >>> > > > > >> >> >>> > > > > >> >> >>> > > > > >> Jeroen Demeyer. >> >>> > > > > >> >> >>> > > > > >> -- >> >>> > > > > >> You received this message because you are subscribed to the >> >>> > > > > >> Google Groups "mpir-devel" group. To post to this group, >> >>> > > > > >> send email to [email protected]. To unsubscribe >> >>> > > > > >> from this group, send email to >> >>> > > > > >> [email protected]. For more options, >> >>> > > > > >> visit this group at >> >>> > > > > >> http://groups.google.com/group/mpir-devel?hl=en. >> >> >> >> -- >> >> You received this message because you are subscribed to the Google >> >> Groups "mpir-devel" group. To post to this group, send email to >> >> [email protected]. To unsubscribe from this group, send email >> >> to [email protected]. For more options, visit >> >> this group at http://groups.google.com/group/mpir-devel?hl=en. > > -- > You received this message because you are subscribed to the Google Groups > "mpir-devel" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/mpir-devel?hl=en. > > -- You received this message because you are subscribed to the Google Groups "mpir-devel" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/mpir-devel?hl=en.
