C Compiler benchmark: gcc 4.6.3 vs. Intel v11 and others
Hello, For those who might be interested, I've recently benchmarked gcc 4.6.3 (and 3.4.2) vs. Intel v11 and Microsoft (in Windows 7) here: http://willus.com/ccomp_benchmark2.shtml willus.com
Re: C Compiler benchmark: gcc 4.6.3 vs. Intel v11 and others
On 1/19/2012 2:59 AM, Richard Guenther wrote: On Thu, Jan 19, 2012 at 7:37 AM, Marc Glisse wrote: On Wed, 18 Jan 2012, willus.com wrote: For those who might be interested, I've recently benchmarked gcc 4.6.3 (and 3.4.2) vs. Intel v11 and Microsoft (in Windows 7) here: http://willus.com/ccomp_benchmark2.shtml http://en.wikipedia.org/wiki/Microsoft_Windows_SDK#64-bit_development For the math functions, this is normally more a libc feature, so you might get very different results on different OS. Then again, by using -ffast-math, you allow the math functions to return any random value, so I can think of ways to make it even faster ;-) Also for math functions you can simply substitute the Intel compilers one (GCC uses the Microsoft ones) by linking against libimf. You can also make use of their vectorized variants from GCC by specifying -mveclibabi=svml and link against libimf (the GCC autovectorizer will then use the routines from the Intel compiler math library). That makes a huge difference for code using functions from math.h. Richard. -- Marc Glisse Thank you both for the tips. Are you certain that with the flags I used Intel doesn't completely in-line the math2.h functions at the compile stage? gcc? I take it to use libimf.a (legally) I would have to purchase the Intel compiler?
Re: C Compiler benchmark: gcc 4.6.3 vs. Intel v11 and others
On 1/18/2012 10:37 PM, Marc Glisse wrote: On Wed, 18 Jan 2012, willus.com wrote: For those who might be interested, I've recently benchmarked gcc 4.6.3 (and 3.4.2) vs. Intel v11 and Microsoft (in Windows 7) here: http://willus.com/ccomp_benchmark2.shtml http://en.wikipedia.org/wiki/Microsoft_Windows_SDK#64-bit_development For the math functions, this is normally more a libc feature, so you might get very different results on different OS. Then again, by using -ffast-math, you allow the math functions to return any random value, so I can think of ways to make it even faster ;-) I use -ffast-math all the time and have always gotten virtually identical results to when I turn it off. The speed difference is important for me.
Re: C Compiler benchmark: gcc 4.6.3 vs. Intel v11 and others
On 1/19/2012 6:29 AM, Richard Guenther wrote: On Thu, Jan 19, 2012 at 3:27 PM, willus.com wrote: On 1/19/2012 2:59 AM, Richard Guenther wrote: On Thu, Jan 19, 2012 at 7:37 AM, Marc Glissewrote: On Wed, 18 Jan 2012, willus.com wrote: For those who might be interested, I've recently benchmarked gcc 4.6.3 (and 3.4.2) vs. Intel v11 and Microsoft (in Windows 7) here: http://willus.com/ccomp_benchmark2.shtml http://en.wikipedia.org/wiki/Microsoft_Windows_SDK#64-bit_development For the math functions, this is normally more a libc feature, so you might get very different results on different OS. Then again, by using -ffast-math, you allow the math functions to return any random value, so I can think of ways to make it even faster ;-) Also for math functions you can simply substitute the Intel compilers one (GCC uses the Microsoft ones) by linking against libimf. You can also make use of their vectorized variants from GCC by specifying -mveclibabi=svml and link against libimf (the GCC autovectorizer will then use the routines from the Intel compiler math library). That makes a huge difference for code using functions from math.h. Richard. -- Marc Glisse Thank you both for the tips. Are you certain that with the flags I used Intel doesn't completely in-line the math2.h functions at the compile stage? Yes. Intel merely comes with its own (optimized) math library while GCC has to rely on the operating system one. Wouldn't it be possible to in-line the standard C math functions in math.h, though, if the correct compiler flags were set? I realize this could be a big task and would potentially have a lot of dependencies on the CPU flag settings, but is it at least conceivable? Or is it highly undesirable for some reason? (I almost don't see how Intel could be so fast on some of those functions without in-lining.) Alternately, is anybody developing an open-source, x86-based or x64-based fast math library (just for standard C math functions--I don't need vector/array/BLAS/etc.) that auto-detects and takes advantage of modern CPU capabilities?
Re: C Compiler benchmark: gcc 4.6.3 vs. Intel v11 and others
On 1/18/2012 10:37 PM, Marc Glisse wrote: On Wed, 18 Jan 2012, willus.com wrote: For those who might be interested, I've recently benchmarked gcc 4.6.3 (and 3.4.2) vs. Intel v11 and Microsoft (in Windows 7) here: http://willus.com/ccomp_benchmark2.shtml http://en.wikipedia.org/wiki/Microsoft_Windows_SDK#64-bit_development For the math functions, this is normally more a libc feature, so you might get very different results on different OS. Then again, by using -ffast-math, you allow the math functions to return any random value, so I can think of ways to make it even faster ;-) Thanks, Marc--I added results from the 64-bit version of MS VC 10 via your link.
