A user reported a slight mismatch between the requested and actual size of the displayed window in the OptiX SDK samples that ship with 3.9. The visible area in the window is up to 8 pixels smaller than requested in both dimensions.
This issue appears to be a bug in the version of freeglut included in SDK/support. We use freeglut for samples on Windows only, not on Linux.
If your application is sensitive to window size, then as a workaround you can download a newer version of freeglut, build it for your platform, and replace the files in the OptiX SDK with your newer files. Follow the build/install instructions in the README files distributed with freeglut. We have confirmed this workaround by running sample6 against freeglut 3.0.0 on a box with Windows 10 and MSVC 2013.
We will update freeglut in the next release of OptiX.