cputime() returns incorrect values

[Anton Dereventsov]

The following simple script generates and multiplies two random 1000-by-1000
matrices for 20 iterations and measures how long (in terms of both the
wall-clock time and the cpu time) each iteration was executing.

Here is the code:


And here is the output that I get:


The wall-clock time measured by tic-toc is believable but the cpu time is
clearly false: sometimes it is negative and sometimes it is exactly 0 or 1.
These particular results were obtained in Octave 4.2.2 on Windows 7 machine
with Intel i7-3610QM cpu but I observed the similar output on Ubuntu 16.04
with Intel Xeon E3-1535M v6.
Coincidentally, in Matlab the same code on the same machines returns
reasonable cpu time.
Is this a bug or am I doing something terribly wrong?

Thanks,
Anton



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