These plots show for each test in stressGraphics, the difference between the
reference file stressGraphics.ref and the results obtain on various machines.
<ul>
<li> A flat line line at 0 means "all good".
<li> The same peak for all the machines means stressGraphics.ref should be adjusted.
<li> Different peaks require a closer look. 
</ul>
May be the macro producing this plot can be run automatically to see immediatly
when something is going wrong.
<p>
<img src="stressGraphics.gif">