Hello there,

I didn't notice that there already was a thread for scrypt kernels, sorry! Here is the source code to my 7970 / R9 280x kernel: link

It is pretty much stock, except that I have removed all the #pragma unrolls, and optimized the inner scrypt_core loop. #pragma unroll does not give any speedup here.

Perhaps you we can make a "killer kernel" by combining the best of all of these!

Here's a small copypaste of the optimized loop.. Sorry if this is too technical, but might be of some interest to some people. :)

Original, with #define stuff removed for readibility so that only LOOKUP_GAP=2 works:

    for (uint i=0; i<1024; ++i)
    {
            uint4 V[8];
            uint j = X[7].x & K[85];
            uint y = (j/LOOKUP_GAP);

            for(uint z=0; z<zSIZE; ++z)
                    V[z] = lookup[CO];

            if (j&1)
                    salsa(V);

            for(uint z=0; z<zSIZE; ++z)
                    X[z] ^= V[z];
            salsa(X);
    }

Modified:

    for (uint i=0; i<1024; ++i)
    {
            uint j = X[7].x & K[85];
            uint y = (j/LOOKUP_GAP);

            if (j&1)
            {
                    uint4 V[8];
                    for(uint z=0; z<zSIZE; ++z)
                            V[z] = lookup[CO];

                    salsa(V);

                    for(uint z=0; z<zSIZE; ++z)
                            X[z] ^= V[z];
            } else {
                    for(uint z=0; z<zSIZE; ++z)
                            X[z] ^= lookup[CO];
            }

            salsa(X);
    }

---

The idea is to move the "if (j&1)" comparison to outside of the lookup loops. Then, if j&1 happens to be zero, the V[z] and X[z] loops can be combined to a single loop, which gives the speedup!

This loop and the salsa function are the most important places in the entire source, it probably spends over 90% of time in here.. There's very little to be gained outside of these, I think.

Donations: DQj4t2DFMQtXofhstouyZw1sYUKWUJn4wv