>Psychtoolbox>PsychTests

MultiWindowLockStepTest([nrwins=2][, separateScreens=0]);

Test if and how many parallel asynchronous window flips
Psychtoolbox can handle on multiple onscreen windows.

This test exercises the asynchronous flip scheduling and
timestamping, aka the Screen(‘AsyncFlipBegin’); and
Screen(‘AsyncFlipCheckEnd’); functions for parallel scheduling
of multiple independent bufferswaps on multiple open onscreen
windows.

‘nrwins’ selects how many onscreen windows to drive in parallel.
If set to [], 2 windows will be used. The i’th window is flipped
at a target rate of one flip every i’th video refresh interval.

Timestamps are collected for all flips and in the end one plot
per window shows how well the flips met their requested deadlines.

If ‘nrwins’ is omitted, a simple test with only two windows is
conducted. One window flips after 10 seconds, the other after 20
seconds.

If the optional parameter ‘separateScreens’ is set to a non-zero
setting, then the different onscreen windows are not opened
on the same display screen 0, but each one on a separate screen.
Performance can differ significantly between one screen and
multi-screen, as the operating system will use very different
underlying algorithms and methods to handle flips on windows,
depending on their placement on different displays or not. Each
operating system will also behave differently.