${\mathbb{L}}_2$ -norm error $N_q$

$N_f$

100

200

300

2000

5.487201e−01

4.770664e−01

5.487201e−01

4000

2.156434e−02

2.176194e−02

2.156434e−02

6000

2.119324e−02

2.013049e−02

1.019324e−02