Monday, November 4, 2013

Shadertoy like OpenCL Kernel Tester

EDIT 2017-11-10: The build environment instructions I've given here are quite out of date, a current one can be found here. Regarding DLL's, MinGW can link directly against them, so there should no longer ever be a need to use dlltool or gendef in anger. END-EDIT

Well I say it's like Shadertoy, but it's nowhere near as good. Either way, it's OpenGL using a texture that's generated in OpenCL, and the CPU isn't getting involved. I've also rewiggled the build system, so now it should theoretically build Windows binaries from Linux, although my Debian Wheezy tests have so far not yielded success. I'm hoping there were bugs in the gcc-4.6 version of mingw64, but there's probably a flag somewhere I'm missing, as my Windows test with the same build config on native Windows version of mingw64 with gcc 4.8 worked a treat.

So GNU/Linux users, to build this type "make". You'll need the OpenCL dev files, and some X11 stuff. It should all be in your repository. It doesn't matter if you install the Nvidia OpenCL headers, or the AMD ones, or the Intel ones. They all work the same, and all speak to each other. Your distro's package manager should have everything on hand, shouldn't be more than a couple of megabytes.

Windows users, to build this type "make". Setting it up to be that easy is a bit of a task. First go download and install the mingw-get-setup.exe, run that and it will do some downloading and some thinking, and then present you with a list of things to install. Down the bottom is MSYS, we need that. We also need the minimal MinGW option at the top for a DLL tool it has, and while we're at it combine it with g++. Once that has finished its thing, (~100Mb later), go download MinGW-w64, and extract it to your C:\ drive. Yes in the root directory, it's a compiler, they're special beasts. Now right click on My computer, or whatever it is these days, and work your way to Advanced Settings and finally to edit your environment variables. Edit your Path, and at the start of it put the text... "c:\mingw64\bin;c:\MinGW\msys\1.0\bin;c:\MinGW\bin;". Now you've got a little bit of unix for your very ownsome. You can open a command prompt and type ls, rm, grep, even bash. Ahem, the last step is installing the OpenCL headers and libraries. I might get in trouble for distributing these files, but it's in good faith so err lets find out. The header files come from Khronos (via Nvidia), the def files were generated against Nvidia's OpenCL.dll and OpenCL64.dll. I'm pretty sure I modified the headers to not complain about using older style OpenCL commands, because that's all my implementation supported. So the files are not official, download this file OpenCL-MinGW.7z, put the contents of the include directory into your c:\mingw64\x86_64-w64-mingw32\include\ directory, and plonk the def files down for a tick, and run this command...
dlltool -l libOpenCL.a -d OpenCL.def -k -A
dlltool -l libOpenCL64.a -d OpenCL64.def -k -A
That will give you the lib.a files you need, stick them in c:\mingw64\x86_64-x64-mingw32\lib\ When the time comes that you want to use more modern OpenCL, you'll have to download the OpenCL SDK from your hardware manufacturer, find their DLL's, and run these commands on them...
gendef OpenCL.dll
gendef OpenCL64.dll
That will give you the .def files you need to give to dlltool. If you're cross compiling from GNU/Linux, dlltool is named "x86_64-w64-mingw32-dlltool". It can be coerced into producing the lib file straight from the DLL, but there's no way I'm going to distribute their DLL's.

Well, here's the link to the code. It builds on Debian Wheezy, and 64bit windows. You can build it in 32bit mode, but I've got datasets too big to fit in 4Gb of RAM. I don't support 32bit for this project. The upper case sigma, "Σ", reloads the OpenCL kernel from disk.

A note about OpenCL. If you've got current video card drivers from Nvidia or AMD then you already have all the OpenCL you need. I expect my OpenCL kernel will disagree with AMDs OpenCL compiler... feel free to fix it AMD owners :-)

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