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What do you mean by major apps? Do you have some reason to believe that apps will suddenly become embarrassingly parallel? Major apps often don't even take full

by davemp 9y ago

What do you mean by major apps? Do you have some reason to believe that apps will suddenly become embarrassingly parallel? Major apps often don't even take full advantage of SIMD instructions on the CPU. As soon as you need a context switch, branching, or fast memory access your GPU is crap. GPUs are only good at _very_ specific workloads.

slededit 9y ago
I used to believe that, until I started to get into cryptocoin mining. There were algorithms that were specifically designed to be GPU resistant and they all were ported and saw significant gains. It was that experience that pushed me to learn how to program these devices. The tooling isn't good enough yet, but there is no question in my mind practically everything will run on a GPU like processor in the future. The speedups are just too tremendous. Intel knows this, which is why they purposely limit PCIe bandwidth.
- IntelMiner 9y ago
  "GPUs are only good at _very_ specific workloads." Let me detail you a completely specific workload citing my own personal experience over objective facts with citations Oh and let me also take a swipe at Intel again without any verifiable evidence
  - slededit 9y ago
    Primecoin is a good example. If you look at the implementation it requires generating a tightly packed bitfield for the sieve and then randomly accessing it after. Lots of synchronization required so you don't overwrite previously set bits are required and the memory accesses are random so its suboptimal for the GPU's memory subsystem. It took under a year for a GPU miner to come out. Having optimized it for Intel in assembly I was convinced it wasn't possible for a GPU to beat it - and yet it happened. It turns out even when used inefficiently a thousand cores can brute force its way through anything.
    - purpleidea 9y ago
      > a thousand cores can brute force its way through anything Cool! Please factor this very large prime for me <insert some RSA prime>
      - slededit 9y ago
        I can't tell what you are mocking... That primecoin exists? That it's POW is finding prime numbers? That it has a GPU miner? http://cryptomining-blog.com/2192-gpu-mining-for-primecoin-xpm-available-but-is-it-worth-it/ http://cryptomining-blog.com/2192-gpu-mining-for-primecoin-x...
    - hvidgaard 9y ago
      > a thousand cores can brute force its way through anything This is so fundamentally wrong that your complete lack of understanding the underlying math is obvious. Let us use 1024bit RSA as the key to bruteforce. If we use the entire universe as a computer, i.e. every single atom in the observable universe enumerate 1 possibility every millisecond, it would take ~6 * 10^211 years to go through them all. In comparison, the universe is less than ~14 * 10^9 years old. And this is for 1024bit, today we use 2048bit or larger.
      - slededit 9y ago
        XPM has nothing to do with finding primes used in RSA, I'm not sure where that came from. It's POW is finding cunningham chains of smaller sized primes. That said I wouldn't be surprised if it could be adapted to find larger primes on a GPU significantly faster than a CPU.
        hvidgaard 9y ago
        It was simply a response to your statement about bruteforcing anything. There is some ways to factor a prime that is much faster than bruteforcing, and yes they work on a GPU. But that has nothing to do with bruteforcing, but clever math.
- coldtea 9y ago
  >I used to believe that, until I started to get into cryptocoin mining. 99% of the apps we use are totally unlike cryptocoin mining. And the style they are written (and more importantly, their function) is even more GPU resistant. >The tooling isn't good enough yet, but there is no question in my mind practically everything will run on a GPU like processor in the future. The speedups are just too tremendous. Don't hold your breath. For one, nobody's porting the thousands of apps we already have and depend on everyday to GPU.
  - slededit 9y ago
    While true in the short term, it should be noted Intel is moving more towards the GPU model with its many slower core CPUs and very wide vector units. There is value in a large core capable of fast out of order execution for control purposes. But data processing can be done much faster with a GPU model. You can even implement explicit speculative execution - simply use a warp for each path and choose at the end. It is very wasteful but can often come out ahead.
    - dom0 9y ago
      No, Intel's approach is very different from GPUs, because Intel has a strong negative interest in making porting to GPUs easy (also, wide vectors are far easier to do in a CPU than a "GPU like model").
- TorKlingberg 9y ago
  Cryptocoin mining is embarrassingly parallel by its nature. You are trying lots of different inputs to a hash function, so you can always run an arbitrary number of them in parallel. There are various ways to reduce the GPU/FPGA/ASIC advantage, like requiring lots of RAM, but the task is still parallel if you have enough RAM. Something like a JavaScript JIT on the other hand is fundamentally hard to parallelize.

by davemp 9y ago

slededit 9y ago

I used to believe that, until I started to get into cryptocoin mining. There were algorithms that were specifically designed to be GPU resistant and they all were ported and saw significant gains. It was that experience that pushed me to learn how to program these devices. The tooling isn't good enough yet, but there is no question in my mind practically everything will run on a GPU like processor in the future. The speedups are just too tremendous. Intel knows this, which is why they purposely limit PCIe bandwidth.

IntelMiner 9y ago
"GPUs are only good at _very_ specific workloads." Let me detail you a completely specific workload citing my own personal experience over objective facts with citations Oh and let me also take a swipe at Intel again without any verifiable evidence
- slededit 9y ago
  Primecoin is a good example. If you look at the implementation it requires generating a tightly packed bitfield for the sieve and then randomly accessing it after. Lots of synchronization required so you don't overwrite previously set bits are required and the memory accesses are random so its suboptimal for the GPU's memory subsystem. It took under a year for a GPU miner to come out. Having optimized it for Intel in assembly I was convinced it wasn't possible for a GPU to beat it - and yet it happened. It turns out even when used inefficiently a thousand cores can brute force its way through anything.
  - purpleidea 9y ago
    > a thousand cores can brute force its way through anything Cool! Please factor this very large prime for me <insert some RSA prime>
    - slededit 9y ago
      I can't tell what you are mocking... That primecoin exists? That it's POW is finding prime numbers? That it has a GPU miner? http://cryptomining-blog.com/2192-gpu-mining-for-primecoin-xpm-available-but-is-it-worth-it/ http://cryptomining-blog.com/2192-gpu-mining-for-primecoin-x...
  - hvidgaard 9y ago
    > a thousand cores can brute force its way through anything This is so fundamentally wrong that your complete lack of understanding the underlying math is obvious. Let us use 1024bit RSA as the key to bruteforce. If we use the entire universe as a computer, i.e. every single atom in the observable universe enumerate 1 possibility every millisecond, it would take ~6 * 10^211 years to go through them all. In comparison, the universe is less than ~14 * 10^9 years old. And this is for 1024bit, today we use 2048bit or larger.
    - slededit 9y ago
      XPM has nothing to do with finding primes used in RSA, I'm not sure where that came from. It's POW is finding cunningham chains of smaller sized primes. That said I wouldn't be surprised if it could be adapted to find larger primes on a GPU significantly faster than a CPU.
      - hvidgaard 9y ago
        It was simply a response to your statement about bruteforcing anything. There is some ways to factor a prime that is much faster than bruteforcing, and yes they work on a GPU. But that has nothing to do with bruteforcing, but clever math.
coldtea 9y ago
>I used to believe that, until I started to get into cryptocoin mining. 99% of the apps we use are totally unlike cryptocoin mining. And the style they are written (and more importantly, their function) is even more GPU resistant. >The tooling isn't good enough yet, but there is no question in my mind practically everything will run on a GPU like processor in the future. The speedups are just too tremendous. Don't hold your breath. For one, nobody's porting the thousands of apps we already have and depend on everyday to GPU.
- slededit 9y ago
  While true in the short term, it should be noted Intel is moving more towards the GPU model with its many slower core CPUs and very wide vector units. There is value in a large core capable of fast out of order execution for control purposes. But data processing can be done much faster with a GPU model. You can even implement explicit speculative execution - simply use a warp for each path and choose at the end. It is very wasteful but can often come out ahead.
  - dom0 9y ago
    No, Intel's approach is very different from GPUs, because Intel has a strong negative interest in making porting to GPUs easy (also, wide vectors are far easier to do in a CPU than a "GPU like model").
TorKlingberg 9y ago
Cryptocoin mining is embarrassingly parallel by its nature. You are trying lots of different inputs to a hash function, so you can always run an arbitrary number of them in parallel. There are various ways to reduce the GPU/FPGA/ASIC advantage, like requiring lots of RAM, but the task is still parallel if you have enough RAM. Something like a JavaScript JIT on the other hand is fundamentally hard to parallelize.