A little program I wrote can be used to analyze the quality of the math
library implementation. It simply computes the real result with a high
precision and determines from this the error of the value the libm
implementation produced. Very easy.
To make the time waiting for the result a bit more interesting the program
displays the error graphically in an updated window. Once the program is
done it writes the plot in a GIF file which then can be used for later
reference.

Homepage:
http://people.redhat.com/drepper/libm/
