Print error distribution for norm

gistfile1.py

import pylab as pl
import numpy as np
import scipy.linalg

nrm2, = scipy.linalg.get_blas_funcs(('nrm2',), np.empty(0, dtype=np.float32))

x_min, x_max = -4., 0
y_min, y_max = 0, 4.
h = 134567e-7
xx, yy = np.meshgrid(np.arange(x_min, x_max, h, dtype=np.float32),
                     np.arange(y_min, y_max, h, dtype=np.float32))
points = np.c_[xx.ravel(), yy.ravel()]

norm_delta = np.empty(points.shape[0], dtype=np.float32)

for i, p in enumerate(points):
    norm_delta[i] = np.abs(nrm2(p) - np.sqrt(np.dot(p, p)))
    #norm_delta[i] = np.abs(nrm2(p) - scipy.linalg.norm(p))

Z = norm_delta.reshape(xx.shape)
pl.contourf(xx, yy, Z)
pl.colorbar()
pl.show()