First, I tried "-march=pentium3 -mfpmath=sse" to no avail - same wrong answer. The is a "rigid plate" analysis for a vibration problem. The correct answer is the plate lattice damps out at -0.414329 @ ~0.5 seconds. With G++ 4.3.4 I'm now getting: -0.43281 @ ~0.9 seconds. Second, I'm simply compiling the source code using g++ <source-file>, the only option "-g". ---Jan On Mon, Jun 13, 2011 at 6:54 AM, Jonathan Wakely <jwakely.gcc@xxxxxxxxx> wrote: > On 13 June 2011 11:24, Jan Chludzinski wrote: >> Just finished compiling some numerical code (developed using the >> Borland C++ compiler) using G++ 4.3.4 (that came with Cygwin 1.7). The >> answers are different from what I get using the Borland compiler >> (circa 2002). I have known correct answers from some NASA code and >> compare against those. >> >> I've transitioned of late to Code::Blocks using the latest MinGW. >> MinGW comes with G++ 4.5.2. I compiled using this compiler and it >> once again works (I get the same answers as the NASA code). >> >> Are there known problems with G++ 4.3.4? >> >> BTW, the original code was infinite looping until I replaced the old style: >> >> for (i=0; i<WHATEVER; i++) .. >> >> with i declared within the routine (i.e., function) with: >> >> for (int i=0; i<WHATEVER; i++) ... > > Are you using x86? Are you telling the compiler to use SSE registers > for floating point instead of the 387 registers? > > Does using "-march=pentium3 -mfpmath=sse" with GCC 4.3.4 give the > expected results? >
