I've never used Amazon EC2, but with this kind of application, I might have to give it a try. Buying a $300 graphics card just to try some GPU programming is ridiculous.

You don't need to buy a $300 graphics card to experiment with GPU programming.

The current and previous generation Intel CPUs (Haswell and Ivy Bridge, respectively) have on-die GPUs which support OpenCL: http://software.intel.com/en-us/articles/intel-sdk-for-openc...

AMD's APUs are quite cheap (~$100) CPU+GPU designs similar to those in the upcoming PS4 and XBox One (though the retail APUs are somewhat less powerful). They've been more-or-less designed specifically around the needs of a heterogenous OpenCL application.

Finally, the last several generations of NVidia cards all support both CUDA and OpenCL; the newer cards do support additional features though. You should be able to pick up a low-end, recent-edition Nvidia GPU for roughly $100.

The new g2.2xlarge instances are $0.650/hour, and the existing cg1.4xlarge are $2.100/hour; so it may make sense to experiment on AWS a bit, then buy your own card for long-term use if you decide to spend more time doing GPU programming.

Sadly, Intel's integrated-GPU OpenCL still doesn't support Linux, and only just started supporting OS X in 10.9 Mavericks[1]. Usually Intel's Linux GPU support is great; I don't know why this is different.

(Intel do have a Linux OpenCL implementation for Xeon CPU cores and Xeon Phi coprocessor[2], which doesn't help me much. On-CPU OpenCL is fine but hardly faster than regular CPU code, and Phi coprocessors aren't very common currently.)

[1] http://forums.macrumors.com/showthread.php?t=1620203 [2] http://software.intel.com/en-us/vcsource/tools/opencl

I take it that you don't play video games on your desktop machine, then.

As I understand it, scrypt is designed to mitigate this: https://en.wikipedia.org/wiki/Scrypt

Except the interface to scrypt is kinda weird so nobody writes sane library bindings for it. (I tried once. I didn't get very far.)

GPUs were rendered useless by ASIC miners, no?

EDIT: Sorry for jumping on the Bitcoin hype train too soon! Many other uses for cracking hashes.

For bitcoins, yes. I believe OP is talking about password hash cracking, a la oclHashcat-plus: http://hashcat.net/oclhashcat-plus/

Aha, you're absolutely right. Shame "cracking hashes" is synonymous to Bitcoins in my mind.

lets go mining.