[geos-devel] 3.9.0beta2

[Paul Ramsey]

> On Dec 3, 2020, at 10:18 PM, Sebastiaan Couwenberg <sebastic at xs4all.nl> wrote:
> 
> On 12/3/20 12:17 AM, Paul Ramsey wrote:
>> without any further ado, here's a beta2 release for your testing pleasure
> 
> testrunner fails on arm64, ppc64el, powerpc, ppc64, riscv64:

Have we ever passed? Perhaps I made a big mistake removing ttmath. 

Anyways, here's what I've learned today, testing on an AWS ARM64 server.

* Still no obvious reason why these platforms shouldn't just work, if they implement IEEE conforming operations on double.
* There's something called FLT_EVAL_METHOD in <cfloat> which might indicate non-IEEE handling of double, but... my test server insists it is FLT_EVAL_METHOD == 0 "evaluate just to the range and precision of the type".

Wondering if there was a brutal hack-around, and noting that "long double" is increasingly a "thing", I took our DD class, and hacked out all the smarts and substituted long double implementations.

https://github.com/pramsey/geos/tree/dd-arm

Interestingly, this implementation passes all the geos::math::DD tests! The ARM64 long double appears to have a full 128bit implementation. Running the same thing on Intel x64 fails a number of tests. This is probably because the long double implementation on x64 has only 80 bits (according to the internet).

Does all this test passing mean that a direct use of long double will work on platforms that support it? Apparently not. The ARM build still fails on quite a few tests of varying sorts, just not on the DD tests.

	 90 - unit-capi-GEOSVoronoiDiagram (Failed)
	140 - unit-linearref-LengthIndexedLine (Failed)
	208 - general-TestCentroid (Failed)
	260 - issue-issue-geos-275 (Failed)
	267 - issue-issue-geos-398 (Failed)
	349 - robust-TestOverlay-pg-list (Failed)

Where does this leave us? With a long research project on ARM64 to track down why these tests fail and/or why the DD implementation fails.

Should we still release? I think so. While ARM and other niche platforms are coming down the pike, it doesn't make sense to delay. GEOS isn't "broken" on those platforms so much as "not perfect".

P.