Performance issues in /src/data (by P3)

[DLPerf]

Hello! I've found a performance issue in dataset.py: batch() should be called before map(), which could make your program more efficient. Here is the tensorflow document to support it.

Detailed description is listed below:

• dataset.batch(FLAGS.batch_size)(line 17) should be called before dataset.map(parse)(line 14).
• dataset2.batch(1)(line 24) should be called before dataset2.map(parse)(line 21).
• dataset.batch(1)(line 39) should be called before dataset.map(parse)(line 36).

Besides, you need to check the function called in map()(e.g., parse called in dataset.map(parse)) whether to be affected or not to make the changed code work properly. For example, if parse needs data with shape (x, y, z) as its input before fix, it would require data with shape (batch_size, x, y, z).

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

[DLPerf]

Hello, I'm looking forward to your reply~