Figure 4.

Overall process of Fast-GPU-PCC. In part (a), fMRI time series is normalized in CPU and transferred to GPU memory. Block size B is computed using Equation (6). If B is larger than N means that the whole computation can be performed in one round which is shown in part (b). In part (b) the whole normalized matrix is multiplied to its transpose and upper triangle is extracted and transferred back to CPU. If block size is computed in part (a) is smaller than N means that only pairwise correlation of B voxels with the rest of voxels can be computed which is shown in part (c). In part (c) after correlation of the first B voxels with the rest of voxels is computed and transferred back to CPU, new block size is computed and this process is repeated multiple time until all pairwise correlations are computed.