On Wed, Jan 14, 2015 at 8:21 PM, Marc Feeley <feeley@iro.umontreal.ca> wrote:
Xcode 6.1.1 was released a little over a month ago, so I decided to do some benchmarking to see how well its C compilers (Apple clang 6.0 and Apple gcc 6.0) compare against GNU gcc 4.9.2 when compiling Gambit.

I configured and built Gambit with

   ./configure --enable-single-host CC="<C_COMPILER>"
   make -j8

I report the build time for each compiler and the execution time of test 4 (which measures the speed of the interpreter, which is indicative of the relative speed of the code generated by Gambit).  Here are the numbers:

  Build          test4         C compiler
  (secs)         (secs)

    60.31        1.30          GNU gcc 4.9.2
  2042.98 (34x)  3.05 (2.3x)   Apple clang 6.0
  1875.56 (31x)  3.08 (2.4x)   Apple gcc 6.0


Thank you for the benchmarks, Marc. It seems that GCC still greatly outperforms Apple's GCC/Clang with Gambit code. Do you have any idea if it is a particular optimization that is producing this divergence, or is just the accumulation of small differences?