Catchup Post

A short collection of interesting links/articles recently:

• Designing Fast Cross-Platform SIMD Vector Libraries plus source code, an interesting read on rolling your own vector libraries. If your looking for a bigger library you can try WildMagic or the Sony maths libraries.
  
• Compiler Cache helps reduce your compile times.
  
• Howard Yeend has an excellent tutorial on K-means clustering (ie: grouping data together, given you know how many groups you want - always a shame..)
  
• New DirectX SDK is out, not sure how this is exciting..
  
• Apple released the iPad, I have no idea if this is good. But I like the alternative, Linux-friendly iPad.
  
• I stumbled upon Alexandre Mutel's blog on 4k programming
  
• I discovered the IEEE has RSS feeds for most journals.
  
• nVidia have named the GF100 chips: GeForce GTX 480 and GeForce GTX 470.
  
• Anandtech have an
  article on GF100 explaining how the CUDA centric card is also great for gaming.
  
• Facebook released HipHop a PHP to C/gcc conversion tool.
  
• Clang self-hosts! I wonder how long until it becomes a serious g++ competitor.
  
• Symbian OS will be open sourced, perhaps a little too late? Still, Nokia are to be admired.
  
• An interesting gallery of processor cache behaviour, unfortunately I don't think the author is fully qualified on this topic. Still, interesting pictures.
  
• The PS3 hypervisor was hacked
  

Finally, a video of the top Tron AI from the Google AI Challenge:

Catchup post

It's been a while since I updated, reason being it is exams/assignments marking period, and I had two GPU industry projects due (3D groundwater flow fluid simulation and a pathfinding/travelling salesman with profits project). 

The biggest news item was that the ACM decided to start (over)enforcing its rules saying that you can not link to preprint and author pages. Thankfully, it started a call-to-arms and prominent pages like Ke-Sen Huang's SIGGRAPH links have been restored. I wonder how many less public pages have silently slipped away. Frankly, I can't wait until the concept of conferences and journals disappear. My websites have always had far more impact that my publications, and it can't be long until the same can be said universally.

A short update with some interesting things in the last while:

• Obama has made a comment about robotics, it's great to hear the field is getting a lot more visible and more support, but I still feel we have a very long way to go to break the western cultures distrust of robotics.
• Sony/Toshiba/IBM CELL is now officially dead.
• There is a new GPU computing community website, just started up: http://gpucomputing.net/
• nVidia's raytracing technology Optix is finally available, but only for next-gen GPU's. The "RealityServer" was also released, to great disappointment to many.
• Tech report has a more detailed report on nVidias new Fermi based GPU's.
• Caustic claims to be selling raytracing accelerators, but they haven't been able to sell me one yet. Smells like vapourware.
• Chromium OS was released. Not sure who wants this? Fast starts haven't been an issue for me since laptop's could sleep. I guess they are aiming for very low prices.
• Peteris Krumins posted a great blog post on the highlights of MIT's algorithms lectures
• Wolfire did an interesting post on generating vertex weights.
• Felix von Leitner put together a very interesting presentation on compiler optimization tricks. It's good proof that compilers are much better than humans for most optimizations, plenty of new things I learnt from this.
• Finally, I saw a link to this paper:Aggregate Dynamics for Dense Crowd Simulation. I've not had a chance to read it yet, but the results look fantastic and the idea is novel. (Using fluid-simulation techniques for representing crowds.) Video below:

   

Apple Mac OS X Utilities

Everyone needs tools to use their PC. I covered the essentials for a Windows PC previously. Some good (free) tools for your Mac:

• StuffIt Expander, your OS X WinRAR/WinZip equivalent.
  
• MacFUSE, this extension enables file systems in user space for the mac. Ever want to read NTFS?
  
• NTFS 3g, the NTFS plug in for macFUSE, no more 'Items could not be moved because XXX cannot be modified'. Why OS X doesn't support NTFS is beyond me. I have been using the NTFS 3g plug in with no problems for about a year now.
  
• Opera, while not a Mac-only utility, having the Opera web browser is essential. Especially when Safari acts up, or you want to use IRC, or bittorrent, or RSS, or email, or anything really. Its an all in one solution.
  
• Parallels, lets you run your bootcamp Windows partition seamlessly inside the mac, and with graphics acceleration to boot. Nifty. While not free, I feel its worthwhile. The free alternative is virtualbox.
  
• Nocturne, this lets you dim, and otherwise change your screen display. Very useful for late night computing.
  
• Small Image, for quick image resizing.
  
• Paintbrush for mac.
  
• Perian and Flip4Mac WMVfor extending media file support by OS X.
  

Plus the usual assortment of VLC, Mplayer, Filezilla, Adobe Reader, etc. A great place to find nifty tools is I use this, for OS X. Tools that get a lot of recommendations, but I don't use much are iStat Pro, VMware, Little Snitch and Transmission. I still haven't figured out if MacPorts or Fink is better, so far, I've had poor experiences with both.

Simple bootloader

Writing your own OS is something every computing person should do at some point. The first step is of course writing a boot loader. This is actually very easy to do under linux.

With a fresh install of ubuntu, make sure you have GCC and related goodies, the other things you will probably want are nasm, and virtual machine like QEMU. Installing these in ubuntu is as simple as:

sudo apt-get install nasm
sudo apt-get install qemu

(you may need to modify your /etc/apt/sources.list - any core ubuntu mirror will do, I used au.archive.ubuntu.com/ubuntu)

Now you probably want to try qemu out before going further, so grab freedos:
http://www.freedos.org/freedos/files/ and grab an iso, I got fdbasecd.iso

Now we create a virtual hard drive to install freedos on to: (do this in the same dir as the iso)

qemu-img create -f raw freedos.img 100M

And then we just boot up qemu:

qemu -localtime freedos.img -cdrom fdbasecd.iso -boot d

Freedos install is a bit obtuse, you need to format the drive to FAT16, exit the formatter, then again to FAT32, but I just pretty much just went with the defaults for everything, afterall, this is just for testing. At then end, you should have a working DOS prompt.

Now that we have QEMU working and we know it, let's try our own boot loader:

[BITS 16]  ; 16 bit code generation
[ORG 0x7C00]  ; ORGin location is 7C00

;Main program
main:   ; Main program label

mov ah,0x0E  ; This number is the number of the function in the BIOS to run.
   ;  This function is put character on screen function
mov bh,0x00  ; Page number (I'm not 100% sure of this myself but it is best
   ;  to leave it as zero for most of the work we will be doing)
mov bl,0x07  ; Text attribute (Controls the background and foreground colour
   ;  and possibly some other options)
   ;  07 = White text, black background.
   ; (Feel free to play with this value as it shouldn't harm 
   ;  anything)
mov al,65  ; This should (in theory) put a ASCII value into al to be 
   ;  displayed. (This is not the normal way to do this)
int 0x10  ; Call the BIOS video interrupt.

jmp $   ; Put it into a coninuous loop to stop it running off into
   ;  the memory running any junk it may find there.

; End matter
times 510-($-$$) db 0 ; Fill the rest of the sector with zeros
dw 0xAA55  ; Boot signature

Save the code to loader.asm, and assemble it with:

nasm loader.asm

Then, we can run our wonderful loader with:

qemu loader

Getting started on the PS3

It's been a while since I set up my PS3 with Linux, but I remember it being a lengthy process. Installing Yellow Dog Linux on the PS3 is relatively straight forward, but then getting the compiler tool chain up and running took a while, mostly in just figuring out what to do. If you only have RCA out on the PS3 you need to install Linux in text-mode, which I remember being a bit dramatic (all the instructions assume you have the GUI environment).

Yellow dog has an package manager called 'yum' (Yellow Dog Updater, Modified).

After the install do a 'yum update'.
(Note, if you are behind a proxy you will need to set the http_proxy variable. For other networking issues 'ifconfig' up/down and 'dhclient' are your friends.)

export http_proxy = "http://username:password@proxy.host.com:port"

Now do a search in yum for any SPU/PPU packages, ie: 'yum search spu' and install the relevant ones. (I can't recall which ones, probably libspe2,spu-binutils,spu-gcc,spu-newlib,ppu-binutils). At the end of this you should have spu-gcc, ppu-embedspu, ppu-ar and the usual suspects (gcc/g++).

You have these different compilers because the SPE and the PPE are completely different processors, it's like having two different computers in one box. So the spu-gcc compiles code only for the SPE, and the 'normal' gcc compiles code for the Power PC.

Obviously the first thing to try is 'hello world' for the PPE, but after that a little SPU/PPU program is what to try. You should be able to find some code on the web, (try the GATECH STI website, or Jeremy's SPE hello world examples) so then you just need to build it:

spu-gcc spu-program.cpp -o spu-program
ppu-embedspu -m32 symbol_name binary_name output-embedded.o
ppu-ar -qcs spulib.a output-embedded.o
g++ ppu-program.cpp -lspe spulib.a -o output

Or, as a concrete example:

spu-gcc spumain.cpp -o spumain
ppu-embedspu -m32 hello_spu spumain hello_spu-embed32.o
ppu-ar -qcs hello_spu.a hello_spu-embed32.o
g++ ppu-program.cpp -lspe hello_spu.a -o helloworld

So in Step 1, we are compiling the SPE program, in Step 2 we are embedding it into an object file by providing the symbol name (eg: extern spe_program_handle_t hello_spu), the binary name (the result from spu-gcc), and the final object file.
In Step 3 we are creating a library from the object, and in Step 4 we are linking it all together.

The entire 'embedding' thing can be a bit confusing, but Alex Chow provides a great overview.

(Note: If you are working with windows, putty and winscp will make your life a lot easier. If your new to linux, try the 'nano' editor (or 'pico'), as opposed to the more powerful, and difficult to master vim. You can make something executable with 'chmod +x filename'. If you stuff up the console, typing 'reset' will save the day)

Good luck. You might find this Cell Cheat Sheet useful.