Optimizing Vector elements swaps using CUDA
- by Orion Nebula
Hi all,
Since I am new to cuda .. I need your kind help
I have this long vector, for each group of 24 elements, I need to do the following:
for the first 12 elements, the even numbered elements are multiplied by -1,
for the second 12 elements, the odd numbered elements are multiplied by -1 then the following swap takes place:
Graph: because I don't yet have enough points, I couldn't post the image so here it is:
http://www.freeimagehosting.net/image.php?e4b88fb666.png
I have written this piece of code, and wonder if you could help me further optimize it to solve for divergence or bank conflicts ..
//subvector is a multiple of 24, Mds and Nds are shared memory
_shared_ double Mds[subVector];
_shared_ double Nds[subVector];
int tx = threadIdx.x;
int tx_mod = tx ^ 0x0001;
int basex = __umul24(blockDim.x, blockIdx.x);
Mds[tx] = M.elements[basex + tx];
__syncthreads();
// flip the signs
if (tx < (tx/24)*24 + 12)
{
//if < 12 and even
if ((tx & 0x0001)==0)
Mds[tx] = -Mds[tx];
}
else
if (tx < (tx/24)*24 + 24)
{
//if >12 and < 24 and odd
if ((tx & 0x0001)==1)
Mds[tx] = -Mds[tx];
}
__syncthreads();
if (tx < (tx/24)*24 + 6)
{
//for the first 6 elements .. swap with last six in the 24elements group (see graph)
Nds[tx] = Mds[tx_mod + 18];
Mds [tx_mod + 18] = Mds [tx];
Mds[tx] = Nds[tx];
}
else
if (tx < (tx/24)*24 + 12)
{
// for the second 6 elements .. swp with next adjacent group (see graph)
Nds[tx] = Mds[tx_mod + 6];
Mds [tx_mod + 6] = Mds [tx];
Mds[tx] = Nds[tx];
}
__syncthreads();
Thanks in advance ..
