errest.py

import numpy as np
from pyiga import bspline, geometry, assemble, approx

def L2ErrEstimator_vf(dim):
    from pyiga.vform import VForm, div, grad, dx, tree_print
    vf = VForm(dim, arity=1)
    u = vf.input('u')
    v = vf.basisfuns()
    Lu = div(grad(u, parametric=True), parametric=True)
    vf.add(Lu**2 * v * dx)
    return vf

kvs = 2 * (bspline.make_knots(2, 0.0, 1.0, 10),)
#geo = geometry.quarter_annulus()
geo = geometry.unit_square()

n = kvs[0].numdofs
u = bspline.BSplineFunc(kvs, approx.interpolate(kvs, lambda x,y: x**2 + 0.5*y**2))

# space of piecewise constants over the cells of the mesh
kvs_0 = 2 * (bspline.make_knots(0, 0.0, 1.0, 10),)

errors = assemble.assemble_vf(L2ErrEstimator_vf(2), kvs_0, geo=geo, u=u)
print(errors)
print(np.sum(errors))
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