On Mon, Jan 4, 2010 at 12:35 AM, Cactus <rieman...@googlemail.com> wrote: > > > On Jan 4, 3:26 am, Case Vanhorsen <cas...@gmail.com> wrote: >> On Sun, Jan 3, 2010 at 12:33 PM, Cactus <rieman...@googlemail.com> wrote: >> >> > On Jan 3, 8:15 pm, Case Vanhorsen <cas...@gmail.com> wrote: >> >> Hello, >> >> >> I discovered an interesting memory allocation behavior on Windows vs. >> >> Linux. I was testing GMPY on 64-bit Windows when I stumbled into this. >> >> GMPY replaces the native MPIR memory allocation routines with Python's >> >> memory allocator. If I enable debugging in GMPY, I get a trace of all >> >> the memory allocation calls. When I ran the following: >> >> >> python -mtimeit -n 1 -r 1 -s "import >> >> gmpy;gmpy.mpz(3)**(2**27);gmpy.set_debug(1)" "a=a*a" 2>temp.txt >> >> >> and look at the output saved in temp.txt, I see that Linux generated >> >> approximately 34 memory manager calls but Windows generates over >> >> 100,000 calls. Most of the Windows allocations are for small (<8K) >> >> chunks of memory while all the Linux requests are for more than 64K. >> >> The performance between Linux and Windows is similar. Could it be that >> >> Windows is not using alloca? >> >> >> I also think I found another memory allocation bug. If I run the above >> >> multiplication repeatedly: >> >> >> python -mtimeit -s "import >> >> gmpy;gmpy.mpz(3)**(2**27);gmpy.set_debug(1)" "a=a*a" 2>temp.txt >> >> >> it will eventually crash. In looking at the debug output, I see a >> >> request to allocate 18446744073709498400 bytes of memory. >> >> >> I tested with both MPIR 1.2.2 and 1.3.0 and get similar behavior. I'm >> >> using a custom version of GMPY with some fixes for size_t vs. long >> >> issues that hasn't been committed but I will try to commit those >> >> changes later today. >> >> > Hi Case >> >> > That is _very_ useful information and may explain why Windows >> > performance lgas that on Linux. >> >> > A long time ago - in GMP days - I had to turn of the use of alloca as >> > I kept getting crashes if I used it. >> >> > I have not tried switching it on in MPIR but I will certainly look at >> > this again. >> >> > But _alloca is now deprecated on Windows and its replacement requires >> > a 'free' procedure that alloca doesn't need. It may hence be quite >> > difficult to take advantage of this in future. It all depends on how >> > GMP/MPIR use alloca. >> >> > Thanks for the debugging! >> >> > Brian >> >> Some additional information. >> >> MPIR 1.2.2 generates approximately 172,000 memory allocator calls. >> MPIR 1.3.0 generates approximately 221,000 memory allocator calls. >> >> The count includes both mp_allocate and mp_free. >> >> Performance numbers: >> Windows x64, MPIR 1.2.2: 3.35 seconds >> Windows x64, MPIR 1.3.0, 3.76 seconds >> Linux, MPIR 1.3.0, 3.05 seconds >> >> Processor is a Core2. >> >> Regarding the mp_allocate failure: it looks like it occurs when trying >> to allocate space for a number larger that 2^32 bits long. > > Does this allocation failure only occur on Windows? Yes. If fails with the stock allocator, too. > > The MPIR settings for memory management on Windows are: > > #define HAVE_ALLOCA 1 > #undef HAVE_ALLOCA_H > #undef WANT_TMP_ALLOCA > #undef WANT_TMP_DEBUG > #undef WANT_TMP_NOTREENTRANT > #define WANT_TMP_REENTRANT 1
#define HAVE_ALLOCA 1 #define HAVE_ALLOCA_H 1 #define WANT_TMP_ALLOCA 1 /* #undef WANT_TMP_REENTRANT */ /* #undef WANT_TMP_NOTREENTRANT */ /* #undef WANT_TMP_DEBUG */ > > What are the normal settings used on a Linux/GCC build? > > Brian > > -- > > You received this message because you are subscribed to the Google Groups > "mpir-devel" group. > To post to this group, send email to mpir-de...@googlegroups.com. > To unsubscribe from this group, send email to > mpir-devel+unsubscr...@googlegroups.com. > 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 mpir-de...@googlegroups.com. To unsubscribe from this group, send email to mpir-devel+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/mpir-devel?hl=en.
