Failing to detect gcc for golden file regeneration

[MarkCallow]

I attempted to regenerate some golden files that have output tolerance enabled and got the message "... not updated on non-primary platform ..."

But I am running under Ubuntu 22.04 and using gcc 11 to compile. Possibly the reason for the failure is that my configuration after selecting "default compilers" shows

CMAKE_CXX_COMPILER /usr/bin/c++
CMAKE_C_COMPILER   /usr/bin/cc

and if I run, e.g, cc --version the output is

cc (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0

while for gcc --version it is

gcc (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0

so you can't see from either the CMake variables or --version output that it is really gcc.

[MarkCallow]

I am surprised to see a tolerance needed with ASTC images. The encoder is supposed to be invariant. But it appears it is not living up to the promise. What was your experience @aqnuep?

[aqnuep]

so you can't see from either the CMake variables or --version output that it is really gcc.

That probably is the reason. Btw, which ASTC images do you see the need for tolerance? What test case are we talking about?

[MarkCallow]

Btw, which ASTC images do you see the need for tolerance? What test case are we talking about?

I didn't see a need for tolerance. I was regenerating golden files dues to an update to the ASTC encoder and got the "... not updated ..." message. The tests in question are create/astc_params.json and create/generate_mipmap.json.

I don't know why there is an outputTolerance in the first. In the second a comment indicates "On apple silicon certain floating point operation causes the lanczos4 filter to sometime be off-by a single unit." The tolerance is set according to which resampling filter is in use, not the output format and ASTC is used in only two of the output cases.

[aqnuep]

Ah, I believe this is related to some floating point precision differences we saw with the ASTC encoder when running on Apple silicon.

[MarkCallow]

Ah, I believe this is related to some floating point precision differences we saw with the ASTC encoder when running on Apple silicon.

As far as I can see the ASTC encoder is producing consistent results. It is the zlib deflator producing different results on x86_64 and Apple Silicon that requires use of outputTolerance in create/astc_params.json.

[aqnuep]

That is interesting... I have no clue how that could happen.