$\tau$

$l^{\infty }$ -error

order

$l^2$ -error

order

$\frac{1}{32}$

3.62e−03

−

1.81e−03

−

$\frac{1}{64}$

8.42e−04

2.11

4.21e−04

2.11

$\frac{1}{128}$

1.99e−04

2.08

9.97e−05

2.08

$\frac{1}{256}$

4.87e−05

2.03

2.43e−05

2.03

$\frac{1}{512}$

1.20e−05

2.02

6.02e−06

2.02