+1 to ripping out in 3.9 and eventually backporting to 3.8 after some testing.
> -----Original Message----- > From: geos-devel [mailto:geos-devel-boun...@lists.osgeo.org] On Behalf > Of Paul Ramsey > Sent: Wednesday, April 15, 2020 5:17 PM > To: GEOS Development List <geos-devel@lists.osgeo.org> > Subject: [geos-devel] Remove ttmath? > > So, we ran into some issues with GEOS 3.8 on a Power architecture, and > based on what tests failed, I suspect the issue is with our use of ttmath. > > In particular, this comment says to me (and just eyeballing what's going on) > that there is some in-baked assumptions about endianness. > > https://github.com/libgeos/geos/blob/master/include/geos/algorithm/ttma > th/ttmathbig.h#L2607-L2609 > > The only reason we're using ttmath is because Mateusz happened to choose > it for his initial experiments on supporting the higher precision code in JTS. > Turns out there's no reason we cannot use exactly the same routines as JTS > does, though, and they have NO ENDIAN assumptions in them, so they'll be > portable. > > The port of the JTS code is here: > > https://github.com/libgeos/geos/pull/303 > > Amazingly, all the regression tests still pass. > > Also, just based on running the full test suite, the DD code seems 5-10% > faster than ttmath. This isn't entirely surprising, since ttmath is an > arbitrary > precision system, while doubledouble uses nothing but standard double math > and the assumption that all double representations and operations are to > IEEE spec. > > I'm going to port the JTS unit tests so we have a little more foundation under > this work, but then I'd like to rip out ttmath in 3.9. > > I'm a little worried that we cannot support big-endian machines in 3.8, so I > think we might consider back-porting this work to 3.8 and switch over to it > for big-endian architectures. > > Paul > > _______________________________________________ > geos-devel mailing list > geos-devel@lists.osgeo.org > https://lists.osgeo.org/mailman/listinfo/geos-devel _______________________________________________ geos-devel mailing list geos-devel@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/geos-devel
