mmcv/docs/en/understand_mmcv/utils.md

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## Utils
### ProgressBar
If you want to apply a method to a list of items and track the progress, `track_progress`
is a good choice. It will display a progress bar to tell the progress and ETA.
```python
import mmcv
def func(item):
# do something
pass
tasks = [item_1, item_2, ..., item_n]
mmcv.track_progress(func, tasks)
```
The output is like the following.
![progress](../_static/progress.*)
There is another method `track_parallel_progress`, which wraps multiprocessing and
progress visualization.
```python
mmcv.track_parallel_progress(func, tasks, 8) # 8 workers
```
![progress](../_static/parallel_progress.*)
If you want to iterate or enumerate a list of items and track the progress, `track_iter_progress`
is a good choice. It will display a progress bar to tell the progress and ETA.
```python
import mmcv
tasks = [item_1, item_2, ..., item_n]
for task in mmcv.track_iter_progress(tasks):
# do something like print
print(task)
for i, task in enumerate(mmcv.track_iter_progress(tasks)):
# do something like print
print(i)
print(task)
```
### Timer
It is convenient to compute the runtime of a code block with `Timer`.
```python
import time
with mmcv.Timer():
# simulate some code block
time.sleep(1)
```
or try with `since_start()` and `since_last_check()`. This former can
return the runtime since the timer starts and the latter will return the time
since the last time checked.
```python
timer = mmcv.Timer()
# code block 1 here
print(timer.since_start())
# code block 2 here
print(timer.since_last_check())
print(timer.since_start())
```