invrnd.m running 
n=2, avgerr=0 
n=2, rnderr=4.16334e-017 
n=4, avgerr=2.39808e-013 
n=4, rnderr=1.04246e-016 
n=8, avgerr=7.31534e-007 
n=8, rnderr=7.86263e-016 
n=16, avgerr=237.479 
n=16, rnderr=3.57e-016 
n=32, avgerr=1.46377e+006 
n=32, rnderr=7.5899e-016 
n=64, avgerr=2.55034e+008 
n=64, rnderr=2.34115e-015 
n=128, avgerr=2.2773e+010 
n=128, rnderr=6.70795e-015 
n=256, avgerr=8.38903e+011 
n=256, rnderr=1.9137e-014