#!/usr/bin/env python
"""
Plot conditions numbers w.r.t. polynomial approximation order of reference
element matrices for various FE polynomial spaces (bases).
"""
from optparse import OptionParser
import time
import numpy as nm
import matplotlib.pyplot as plt
from sfepy import data_dir
from sfepy.base.base import output, assert_
from sfepy.fem import Mesh, Domain, Field, FieldVariable, Material, Integral
from sfepy.terms import Term
from sfepy.solvers import eig
usage = '%prog [options]\n' + __doc__.rstrip()
help = {
'basis' :
'name of the FE basis [default: %default]',
'max_order' :
'maximum order of polynomials [default: %default]',
'matrix_type' :
'matrix type, one of "elasticity", "laplace" [default: %default]',
'geometry' :
'reference element geometry, one of "2_3", "2_4", "3_4", "3_8"'
' [default: %default]',
}
[docs]def main():
parser = OptionParser(usage=usage, version='%prog')
parser.add_option('-b', '--basis', metavar='name',
action='store', dest='basis',
default='lagrange', help=help['basis'])
parser.add_option('-n', '--max-order', metavar='order', type=int,
action='store', dest='max_order',
default=10, help=help['max_order'])
parser.add_option('-m', '--matrix', metavar='type',
action='store', dest='matrix_type',
default='laplace', help=help['matrix_type'])
parser.add_option('-g', '--geometry', metavar='name',
action='store', dest='geometry',
default='2_4', help=help['geometry'])
options, args = parser.parse_args()
dim, n_ep = int(options.geometry[0]), int(options.geometry[2])
output('reference element geometry:')
output(' dimension: %d, vertices: %d' % (dim, n_ep))
n_c = {'laplace' : 1, 'elasticity' : dim}[options.matrix_type]
output('matrix type:', options.matrix_type)
output('number of variable components:', n_c)
output('polynomial space:', options.basis)
output('max. order:', options.max_order)
mesh = Mesh.from_file(data_dir + '/meshes/elements/%s_1.mesh'
% options.geometry)
domain = Domain('domain', mesh)
omega = domain.create_region('Omega', 'all')
orders = nm.arange(1, options.max_order + 1, dtype=nm.int)
conds = []
order_fix = 0 if options.geometry in ['2_4', '3_8'] else 1
for order in orders:
output('order:', order, '...')
field = Field.from_args('fu', nm.float64, n_c, omega,
approx_order=order,
space='H1', poly_space_base=options.basis)
to = field.approx_order
quad_order = 2 * (max(to - order_fix, 0))
output('quadrature order:', quad_order)
integral = Integral('i', order=quad_order)
qp, _ = integral.get_qp(options.geometry)
output('number of quadrature points:', qp.shape[0])
u = FieldVariable('u', 'unknown', field, n_c)
v = FieldVariable('v', 'test', field, n_c, primary_var_name='u')
m = Material('m', lam=1.0, mu=1.0)
if options.matrix_type == 'laplace':
term = Term.new('dw_laplace(m.mu, v, u)',
integral, omega, m=m, v=v, u=u)
n_zero = 1
else:
assert_(options.matrix_type == 'elasticity')
term = Term.new('dw_lin_elastic_iso(m.lam, m.mu, v, u)',
integral, omega, m=m, v=v, u=u)
n_zero = (dim + 1) * dim / 2
term.setup()
output('assembling...')
tt = time.clock()
mtx, iels = term.evaluate(mode='weak', diff_var='u')
output('...done in %.2f s' % (time.clock() - tt))
mtx = mtx[0][0, 0]
try:
assert_(nm.max(nm.abs(mtx - mtx.T)) < 1e-10)
except:
from sfepy.base.base import debug; debug()
output('matrix shape:', mtx.shape)
eigs = eig(mtx, method='eig.sgscipy', eigenvectors=False)
eigs.sort()
# Zero 'true' zeros.
eigs[:n_zero] = 0.0
ii = nm.where(eigs < 0.0)[0]
if len(ii):
output('matrix is not positive semi-definite!')
ii = nm.where(eigs[n_zero:] < 1e-12)[0]
if len(ii):
output('matrix has more than %d zero eigenvalues!' % n_zero)
output('smallest eigs:\n', eigs[:10])
ii = nm.where(eigs > 0.0)[0]
emin, emax = eigs[ii[[0, -1]]]
output('min:', emin, 'max:', emax)
cond = emax / emin
conds.append(cond)
output('condition number:', cond)
output('...done')
plt.figure(1)
plt.semilogy(orders, conds)
plt.xticks(orders, orders)
plt.xlabel('polynomial order')
plt.ylabel('condition number')
plt.grid()
plt.figure(2)
plt.loglog(orders, conds)
plt.xticks(orders, orders)
plt.xlabel('polynomial order')
plt.ylabel('condition number')
plt.grid()
plt.show()
if __name__ == '__main__':
main()
