I just made a wonderful discovery today as a result of a thread on the MinGW/MSYS mailing list where a guy claimed that he generated consistent unrounded floating-point results with gcc and other compilers (Borland and MSVC?) for massive (many hours) floating-point computations regardless of the optimizations for those compilers (so long as he stuck with the usual simple numerical -O optimizations and didn't use exotic optimization parameters). That contradicted all I "knew" from our experience several years ago where even changing the simple optimization level from -O0 to -O1 affected our PostScript results. So I made a new test today and indeed the -O0 and -O3 results agree exactly for all our standard C examples using gcc (Debian 4.9.2-10). So that result is consistent with his. Furthermore, if his more general result really does hold up for all C compilers accessible to us, that is going to be a huge breakthrough in our testing (i.e., we should be able to generate and distribute a tarball of SVG or PostScript results that every platform should be able to reproduce exactly).
Anyhow, after the current release is completed I plan to circulate such a tarball to developers here to see whether we do really get the same C results for all our standard examples for all compilers accessible to us. And if that consistency is confirmed, then some substantial changes in our testing procedure should be implemented that take advantage of that new floating-point consistency capability of C compilers. Alan __________________________ Alan W. Irwin Astronomical research affiliation with Department of Physics and Astronomy, University of Victoria (astrowww.phys.uvic.ca). Programming affiliations with the FreeEOS equation-of-state implementation for stellar interiors (freeeos.sf.net); the Time Ephemerides project (timeephem.sf.net); PLplot scientific plotting software package (plplot.sf.net); the libLASi project (unifont.org/lasi); the Loads of Linux Links project (loll.sf.net); and the Linux Brochure Project (lbproject.sf.net). __________________________ Linux-powered Science __________________________ ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Plplot-devel mailing list Plplot-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/plplot-devel
