GpuTest is a cross-platform GPU stress test and benchmarking utility, based
on OpenGL.  It comes with a number of different tests, including the famous
stress test based on FurMark (OpenGL 2.1 or 3.2), a tessellation test based
on TessMark (OpenGL 4.0), and geometry instancing test (OpenGL 3.3).

An optional GUI (graphical user interface) program made with Python/Tkinter
is available since GpuTest version 0.6.0.