Performance issue in the definition of __main__, examples/circular_ode_demo.py(P1)

[DLPerf]

Hello, I found a performance issue in the definition of __main__, examples/circular_ode_demo.py, tf.reduce_mean(tf.abs(pred_y - true_y)) will be calculated repeatedly during program execution, resulting in reduced efficiency. I think pred_y in line 185 and loss should be created before the loop.

Looking forward to your reply. Btw, I am very glad to create a PR to fix it if you are too busy.