GPUVerify is a tool for formal analysis of GPU kernels written in OpenCL and CUDA. The tool can prove that kernels are free from certain types of defect, such as data races and bugs – useful feedback for any GPU-programmer. StreamComputing have an online version of the tool that you can play around with to test your kernels at: http://streamcomputing.eu/knowledge/tools/gpuverify/
To learn more about GPU Verify itself watch these videos: