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"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

"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.
      - Dylan16807 9y ago
        The statement was about the relative speed of a thousand dumb cores vs. a couple really good cores. Not about absolute speed.
        hvidgaard 9y ago
        The statement was stating an absolute. Algorithmic complaxity matters more than the speed of the computing hardware. Obviously, more power means you can compute more, but not everything.
        slededit 9y ago
        That's a very uncharitable reading of what I wrote. The topic of the conversation was GPU performance vs CPU performance. Despite being less flexible, the sheer quantity of execution units more than makes up for it. But no, I suppose its more likely I was really saying GPUs aren't bounded by the limits of the universe.
        hvidgaard 9y ago
        The context is Primecoin and ability to find primes. Prime factorization is related to that, and it would be obvious to read your statement in absolut for that context and it's relation. At least I did.
- imtringued 9y ago
  But you don't have thousands of cores. You have a medium amount of cores (64 in the latest Vega 64 GPU) with a high amount of ALUs (and threads) per core. When the GPU executes an instruction for a thread it looks if the other threads execute the same instruction and then utilises all ALUs at once. This is great for machine learning and HPC where you often just have a large matrix or array of the same datatype that you want to process but most of the time this isn't the case.

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.
    - Dylan16807 9y ago
      The statement was about the relative speed of a thousand dumb cores vs. a couple really good cores. Not about absolute speed.
      - hvidgaard 9y ago
        The statement was stating an absolute. Algorithmic complaxity matters more than the speed of the computing hardware. Obviously, more power means you can compute more, but not everything.
        slededit 9y ago
        That's a very uncharitable reading of what I wrote. The topic of the conversation was GPU performance vs CPU performance. Despite being less flexible, the sheer quantity of execution units more than makes up for it. But no, I suppose its more likely I was really saying GPUs aren't bounded by the limits of the universe.
        hvidgaard 9y ago
        The context is Primecoin and ability to find primes. Prime factorization is related to that, and it would be obvious to read your statement in absolut for that context and it's relation. At least I did.
imtringued 9y ago
But you don't have thousands of cores. You have a medium amount of cores (64 in the latest Vega 64 GPU) with a high amount of ALUs (and threads) per core. When the GPU executes an instruction for a thread it looks if the other threads execute the same instruction and then utilises all ALUs at once. This is great for machine learning and HPC where you often just have a large matrix or array of the same datatype that you want to process but most of the time this isn't the case.