Parallel spatial matching for object retrieval implemented on GPU

Spatial matching for object retrieval is often time-consuming and susceptible to viewpoint changes. To address this problem, we propose a novel spatial matching method and implement it on modern GPU in parallel. Unlike previous spatial matching methods, in which the affine transformation estimation is based on the gravity vector assumption, our method abandons this strong assumption by matching the ACNs (affine covariant neighbors) of corresponding local regions and estimating affine transformation from a single pair of corresponding local regions. To speed up the process, we implement the method on modern GPU in parallel. Computations are distributed evenly to threads with load balancing, and the memory accesses are optimized and bitmap based parallel scan is exploited. Experimental results demonstrate that our method is more robust and more efficient than previous methods especially when the viewpoints are changed, and the parallel implementation on GPU obtains ten times speedup.