GPU miners example works now, if slowly.

[fasiha]

Addresses #11. Results:

Mined a block on the CPU, nonce: 695822 (time: 0.011s)
Mined a block on the GPU, nonce: 695822 (time: 0.055s)

Is the GPU so much slower because it only stops after all monkeys have done their thing (unlike the CPU which stops once it mines the block), or because I’m doing something inefficient in GLSL-land? (I am total n00b to GLSL.)

Feedback welcome.

[VictorTaelin]

I'm really busy, will be reviewing the cause for the slowdown soon. I've briefly looked the code and looks like you did a great job. Thank you very much.

[VictorTaelin]

Oh, that is okay. As I said on the comments, the mod function on GLSL seems not to work for big numbers (mod(bhash * nonce, pow(2.0, 31.0)). So, if we increase the difficulty too much, it gives wrong results. Since the difficulty is set to very small, the CPU does it better as the GPU startup overhead doesn't compensate. If you really needed to mine, you must write safe Uint32 mod (and similar) functions on GLSL, but that is too much effort for just an example. The searchFor987654321 was made to benchmark that kind of program (it just increments nonces instead of hashing).