meaning of function flush()

[AlbertoPresta]

Hi,

What is the meaning of function encoder.flush() in line 644 of google.py module?

Thanks in advance for answer,
Alberto

[YodaEmbedding]

Flushing a buffer means emptying its contents, and using these contents to do some work. For instance, try running:

import subprocess

with open("file.txt", "w") as f:
    print("This line was flushed.", file=f)
    f.flush()

    print("$ cat file.txt")
    subprocess.run(["cat", "file.txt"])

    print("This line will not show until flushed.", file=f)
    print("This line is also buffered.", file=f)

    print("$ cat file.txt")
    subprocess.run(["cat", "file.txt"])

    # f.flush()  # Automatically called when file is closed, or if buffer grows too large.

Output:

$ cat file.txt
This line was flushed.
$ cat file.txt
This line was flushed.

In CompressAI, the underlying encoder is buffering the intermediate symbols that it will encode. When encoder.flush() is called, it converts all these into an output bitstream. In google.py, we're not really using its buffering capabilities much since we immediately flush it after a single call to encode_with_indexes (which corresponds to "print" in the example above).