## Compatibility GCC Installed

One of the more frustrating facts about Debian / Stretch is that its maintainers have broken with tradition, by no longer providing any compatibility versions of the main compilers, GCC, CPP and C++, which provide CC and C++ -language support, useful in 90% (+) of all programming that takes place. Instead, Debian / Stretch provides GCC / CPP / C++ version 6.3 alone. What I had already written about was, that the version of the CUDA Run-Time and Toolkit available from the standard repositories, has remained v8.0.44 for the time being. This CUDA Version does not support CC or C++ version 6 because version 6 of these compilers is too high!

One way in which power-users could try to remedy this situation would be, to install some sort of compatibility version of CC / C++, even though none is offered in the standard repositories. But, when we try to custom-compile let’s say, GCC v5.3, which would already be low enough for CUDA 8.0.44 to support, we find that GCC 6.3 is just plain unable to compile GCC 5.3, no matter what.

And so another way to solve the same problem can be, to add the old Debian Jessie / Oldstable repositories to our sources list, and then just to install from there.

I find this to be an extremely bad idea.

First of all, Debian differs from Ubuntu, in that Debian never provided GCC 5.3. In Debian / Jessie, what we got was GCC 4.8, or maybe even v4.9. But more importantly, simply sandwiching two incompatible repositories together can create a fatal set of problems.

What I was finally able to do, was just to download roughly a dozen packages as binaries, from the Debian Repository Web-site, which finally provided GCC, CPP and C++ v4.8. The path I took required that I run into the error message numerous times that dependencies could not be satisfied, because under Debian, neither ‘/usr/bin/gcc’ nor ‘/usr/bin/c++’ are provided by a single, binary package. Each is provided by packages, that depend uniquely on other packages, that are also not in the repositories.

Further, once the power-user has in fact installed binaries, after making sure that none of their file-names overlap, he must also create a system of Debian Alternatives, that allow him to switch between compilers easily. The problem with that is the fact that because, under Debian / Stretch, no provision was ever made by Package Maintainers for alternatives to exist, automatic mechanisms have also not been provided, to install ‘Link Groups’. The Link Groups ‘cc’, ‘cpp’ and ‘c++’ exist, but only in such a way as to provide one executable each.

As I was doing my best to install the Link Groups, I made a mistake, which simply over-wrote ‘/usr/bin/gcc’ with a different symlink, and which therefore forced me to (1) delete the link-group, and (2) reinstall GCC 6.3 from the package manager. After that, a new attempt to set up the link-groups succeeded:


dirk@Phosphene:~$su Password: root@Phosphene:/home/dirk# update-alternatives --config cc There are 2 choices for the alternative cc (providing /usr/bin/cc). Selection Path Priority Status ------------------------------------------------------------ * 0 /usr/bin/gcc-6 20 auto mode 1 /usr/bin/gcc-4.8 10 manual mode 2 /usr/bin/gcc-6 20 manual mode Press to keep the current choice[*], or type selection number: root@Phosphene:/home/dirk# update-alternatives --config cpp There are 2 choices for the alternative cpp (providing /usr/bin/cpp). Selection Path Priority Status ------------------------------------------------------------ * 0 /usr/bin/cpp-6 20 auto mode 1 /usr/bin/cpp-4.8 10 manual mode 2 /usr/bin/cpp-6 20 manual mode Press to keep the current choice[*], or type selection number: root@Phosphene:/home/dirk# update-alternatives --config c++ There are 2 choices for the alternative c++ (providing /usr/bin/c++). Selection Path Priority Status ------------------------------------------------------------ * 0 /usr/bin/g++-6 20 auto mode 1 /usr/bin/g++-4.8 10 manual mode 2 /usr/bin/g++-6 20 manual mode Press to keep the current choice[*], or type selection number: root@Phosphene:/home/dirk# exit exit dirk@Phosphene:~$



Note: The first link above, named ‘cc’, has a corresponding slave-link named ‘gcc’, thereby forming the only real ‘Link Group’. The others are just plain Links.

I am reasonably certain that none of these link-groups are broken. But what my reader should be able to infer from what I’ve written, is that It would be a hare-brained attempt, to duplicate what I’ve done, entirely based on this blog posting.

(Edit 5/03/2019, 11h45 : )

Just to prove how hare-brained this idea really is, I just uninstalled the alternative compilers, and replaced them with the GCC / CPP / C++ tool-chain, version 4.9, and made that part of the update-alternatives system as above! (:3)

(End of Edit.)

So what does this provide me with (hopefully)?

(Updated 5/02/2019, 12h15 … )

## Update to Computer Phosphene Last Night

Yesterday evening, a major software update was received to the computer which I name ‘Phosphene’, putting its Debian version to 9.9 from 9.8. One of the main features of the update was, an update to the NVIDIA graphics drivers, as installed from the standard Debian repositories, to version 390.116.

This allows the maximum OpenGL version supported by the drivers to be 4.6.0, and for the first time, I’m noticing that my hardware now limits me to OpenGL 4.5 .

The new driver version does not come with an update to the CUDA version, the latter of which merits some comment. When users install CUDA to Debian / Stretch from the repositories, they obtain run-time version 8.0.44, even though the newly-updated drivers support CUDA all the way up to version 9. This is a shame because CUDA 8.0 cannot be linked to, when compiling code on the GCC / CPP / C++ 6 framework, that is also standard for Debian Stretch. When we want code to run on the GPGPU, we can just load the code onto the GPU using the CUDA run-time v8.0.44, and it runs fine. But if we want to compile major software against the headers, we are locked out. The current Compiler version is too high, for this older CUDA Run-Time version. (:1) (:4)

But on the other side of this irony, I just performed an extension of my own by installing ‘ArrayFire‘ v3.6.3 , coincidentally directly after this update. And my first attempt to do so involved the binary installer that ships with its own CUDA run-time libraries, those being of version 10. Guess what, Driver version 390 is still not high enough to accommodate Run-Time version 10. This resulted in a confusing error message at first, stating that the driver was not high enough, apparently to accommodate the run-time installed system-wide, which would have been bad news for me, as it would have meant a deeply misconfigured setup – and a newly-botched update. It was only after learning that the binary installer for ArrayFire ships with its own CUDA run-time, that I was relieved to know that the system-installed run-time, was fine…

(Updated 4/29/2019, 20h20 … )

## About how I won’t be doing any ‘ASL’ computing soon.

There exists an Open-Source code library named ‘ASL’, which stands for “Advanced Simulation Library“. Its purpose is to allow application-designers who don’t have to be deep experts at writing C++ code, to perform fluid simulations, but with the volume-based simulations running on the GPU of the computer, instead of on the CPU. This can also lead people to say, that ‘ASL’ is hardware-accelerated.

Last night I figured, that ‘ASL’ should run nicely on the Debian / Stretch computer I name ‘Plato’, because that computer has a GeForce GTX460 graphics card, which was considered state-of-the-art in 2011. But unfortunately for me, ‘ASL’ will only run its simulations correctly, if the GPU delivers ‘OpenCL’, version 1.2 or greater. The GeForce 460 graphics card is only capable of OpenCL 1.1, and is therefore no longer state-of-the-art by far.

Last night, I worked until exhausted, trying various solutions, in hopes that maybe the library had not been compiled correctly – I custom-compiled it, after finding out that the simulations were not running correctly. I also looked in to the possibility, that maybe I had just not been executing the sample experiments correctly. But alas, the problem was my ‘weak’ graphics card, that is nevertheless OpenGL 4 -capable.

As an alternative to using ‘ASL’, Linux users can use the Open-Source program-set called ‘Elmer‘. They run on the CPU.

Further, there is an associated GUI-application called ‘ParaView‘, the purpose of which is to take as input, volume-based geometries and arbitrary values – i.e., fluid states – and to render those with some amount of graphics finesse. I.e., ‘ParaView’ can be used to post-process the simulations that were created with ‘ASL’ or with ‘Elmer’, into a presentable visual. The version of ‘ParaView’ that installs from the package-manager under Debian / Stretch, ‘5.1.x’ , works fine. But for a while last night, I did not know whether problems that I was running in to were actually due to ‘ASL’ or to ‘ParaView’ misbehaving. And so what I also did, was to custom-compile ‘ParaView’, to version 5.5.2 . And if one does this, then the next problem one has, is that ParaView v5.5.2 requires VTK v7, while under Debian / Stretch, all we have is VTK v6.3 . And so on my platform, version 5.5.2 of ParaView encounters problems, in addition to ‘ASL’ encountering problems. And so for a while I had difficulty, identifying what the root causes of these bugs were.

Finally, the development branch, custom-compiled version of ‘Elmer’ and package-manager-installed ‘ParaView’ v5.1.x will serve me fine.

Dirk