  We developed a high-speed image reduction pipeline using Graphics Processing
Units (GPUs) as hardware accelerators. Astronomers desire detecting EM
counterpart of gravitational-wave sources as soon as possible for sharing
positional information to organize systematic follow-up observations.
Therefore, high-speed image processing is important. We developed a new image
reduction pipeline for our robotic telescope system, which uses a GPU via a
Python package CuPy to achieve high-speed image processing. As a result, the
processing speed was increased by more than a factor of forty to that of the
current pipeline, while maintaining the same functions.
