  The MWA is a next-generation radio interferometer under construction in
remote Western Australia. The data rate from the correlator makes storing the
raw data infeasible, so the data must be processed in real-time. The processing
task is of order ~10 TFLOPS. The remote location of the MWA limits the power
that can be allocated to computing. We describe the design and implementation
of elements of the MWA real-time data processing system which leverage the
computing abilities of modern graphics processing units (GPUs). The matrix
algebra and texture mapping capabilities of GPUs are well suited to the
majority of tasks involved in real-time calibration and imaging. Considerable
performance advantages over a conventional CPU-based reference implementation
are obtained.
