Option variable
rombergabsDefault value: 0.0
The accuracy of romberg is governed by the global variables
rombergabs and rombergtol.
romberg terminates successfully when
the absolute difference between successive approximations is less than rombergabs,
or the relative difference in successive approximations is less than rombergtol.
Thus when rombergabs is 0.0 (the default)
only the relative error test has any effect on romberg.