POV-Ray : Newsgroups : povray.beta-test : Technical verification build "v3.8.0-beta.668" - Unix package! : Re: Technical verification build "v3.8.0-beta.668" - Unix package! Server Time
28 Sep 2021 07:29:56 EDT (-0400)
  Re: Technical verification build "v3.8.0-beta.668" - Unix package!  
From: William F Pokorny
Date: 24 Jun 2021 09:21:54
Message: <60d486f2$1@news.povray.org>
On 6/23/21 11:20 PM, Thomas Debe wrote:
> 1.) Problem:
> Build povunix-v3.8.9-beta.668.tar.gz Compiler clang-x:
> Optimized Noise-Functions not compiled !
> Clang defines __clang__ Not __GNUC__
> 
> Solution :
> File :  unix/povconfig/syspovconfig.h
> 
> Z 169ff:  #if defined (__clang__)
>              #define HAVE_ASM_AVX
>              #define HAVE_ASM_AVX2
>              #define HAVE_ASM_FMA3
>              #define HAVE_ASM_FMA4
>           #endif
> 
> Z. 179: // most notably platform-specific optimized implementations.
>          #if defined (__GNUC__) || defined(__clang__)

With respect to this, remember POV-Ray is, on unix/linux, a gnu tooling 
targeted build. If using clang, it would be normal to use the 
clang/clang++ flag '-fgnuc-version=5', say if your clang supports all 
the variations. Though using my povr branch, I do get the intel hand 
optimizations on my i3 doing clang compiles.

---
Aside: Long been on my list to look at some of the disable build 
configurations Christoph added when enabling the noise optimizations for 
unix/linux. This a new to v3.8 feature for unix/linux users!

It all works to what I can test without and AMD CPU. For example, to 
turn off all the AMD/Intel hand optimizations you build with the 
compiler flags:

-DDISABLE_OPTIMIZED_NOISE_AVXFMA4 -DDISABLE_OPTIMIZED_NOISE_AVX2FMA3 and 
-DDISABLE_OPTIMIZED_NOISE_AVX

On my i3 which has avx I then get a portable avx instruction optimized 
noise(1). If I want that gone too - so I only get whatever optimizations 
the compiler would give me I add:

-DDISABLE_OPTIMIZED_NOISE_AVX_PORTABLE

Pretty cool. I've never set it up, but these configurations make it 
relatively easy to create a set load modules with the differing 
optimizations. We could, for example, look for more of the optimized 
noise performance outliers - scenes where the hand optimized code looked 
to be somewhat slower.

Bill P.

(1) - For those with avx2, wonder what OPTIMIZED_NOISE_AVX2_PORTABLE 
might offer...


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