On 27 out, 15:24, Mears <[EMAIL PROTECTED]> wrote: > On Oct 27, 5:00 am, Jeff Schwab <[EMAIL PROTECTED]> wrote: > > > > > On Oct 26, 9:49 pm, Mears <[EMAIL PROTECTED]> wrote: > > > > I spent some time profiling exception performance on Solaris 10 with > > > Sun's CC and two different versions of g++. The setup was a class > > > that threw an exception (an int value) in its constructor if an > > > argument was out of range. The main program basically dynamically > > > allocated objects of that type a variable number of times. I tested > > > three different scenarios: > > > > 1. Exception not thrown, and no try/catch in the main program > > > 2. Exception not thrown, and a try/catch surrounding the "new" > > > statement. > > > 3. Exception thrown, and a try/catch surrounding the "new" statement > > > (catch was a no-op). > > > > The compilers I used were (information from version options): > > > CC - Sun C++ 5.8 Patch 121017-10 2007/02/21 > > > g++ - 3.4.3 (csl-sol210-3_4-brach+sol_rpath) > > > g++ - 2.95.3 20010315 (release) > > > > The performance of g++ when not throwing an exception (scenarios 1 & > > > 2) was acceptable IMO. CC definitely had an edge, but all were > > > quick. However, when I started testing scenario 3, g++ was > > > horrendous. For example , when calling the constructor 1,000,000 > > > times (and thus throwing 1,000,000 exceptions), on average CC > > > completed the test program in 2.3 seconds, g++ 2.95.3 completed in > > > 15.9 seconds, and g++ v3.4.3 completed in 22.1 seconds. I was > > > extremely surprised to see g++ nearly 10 times slower at handling > > > throw statements than CC, especially since it was much closer with > > > exception overhead when not throwing. > > > That is the intent. Typical exception (forgive the oxymoron) support > > is heavily optimized for the case in which exceptions are not thrown, > > because that case should be much more common. The point is that your > > program isn't penalized for being robust. If something actually goes > > wrong, the call stack should be unwound to the point where an > > appropriate handler can address the problem. This isn't something > > that should be happening repeatedly in a loop. > > I understand that exception handling is optimized for the case where > exceptions are not thrown, and CC did better than g++ in that area as > well, so it's not like CC cut corners to improve performance when > exceptions are thrown. To me it seems like g++ could use some > improvement in this area.
Maybe it has. You tested a very old version. Try your benchmarks with GCC 4.2 and GCC trunk (which will be version 4.3). -- Pedro Lamarão _______________________________________________ help-gplusplus mailing list help-gplusplus@gnu.org http://lists.gnu.org/mailman/listinfo/help-gplusplus
