  We revisit the implementation of iterative solvers on discrete graphics
processing units and demonstrate the benefit of implementations using extensive
kernel fusion for pipelined formulations over conventional implementations of
classical formulations. The proposed implementations with both CUDA and OpenCL
are freely available in ViennaCL and are shown to be competitive with or even
superior to other solver packages for graphics processing units. Highest
performance gains are obtained for small to medium-sized systems, while our
implementations are on par with vendor-tuned implementations for very large
systems. Our results are especially beneficial for transient problems, where
many small to medium-sized systems instead of a single big system need to be
solved.
