> On Dec 4, 2020, at 4:16 PM, Paul Ramsey <pram...@cleverelephant.ca> wrote:
>
>
>
>> On Dec 4, 2020, at 4:08 PM, Paul Ramsey <pram...@cleverelephant.ca> wrote:
>>
>>
>>
>>> On Dec 4, 2020, at 1:10 PM, Paul Ramsey <pram...@cleverelephant.ca> wrote:
>>>
>>>
>>>> On Dec 3, 2020, at 10:18 PM, Sebastiaan Couwenberg <sebas...@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.
>>
>> Since this was a finite set of test failures and I was wondering if these
>> failures were "real" or "tiny", I started going through them and the Voronoi
>> failures seemed to fall into the "tiny" category. There was/is clearly a
>> double precision equality test in the code that is returning true on one
>> platform and false on another, because the answers are very very similar.
>>
>> When I moved onto unit-linearref-LengthIndexedLine test, there wasn't any
>> good printed debugging, so I broke out the debugger, and I had to rebuild in
>> Debug mode. Guess what:
>>
>> 100% tests passed, 0 tests failed out of 364
>>
>> Yep, with the hardware long double for precision and in debug mode every
>> test passes. So the problems on ARM64 are even *more* awful to figure out.
>> Something about the optimized release build is different enough to matter.
>
> In fact, a debug build passes all tests straight off master, no replacement
> work on DD required. This perhaps explains my success testing GEOS on ARM
> earlier.
Narrowing the situation further: I can do a standard release build using CLANG
and it passes all tests. This problem is only associated with GCC and the flags
it uses for a release build. Not clear which ones are the problem though, they
all look pretty anodyne.
P
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