Compute metric per image and handler mutex in DistributedDataParallel

❓ Questions/Help/Support

Hi @vfdev-5 ,

I am writing an ignite handler to write the segmentation metrics of every image into 1 CSV file as the summary, for example:

metrics.csv:
/data/spleen/image_1    0.85
/data/spleen/image_2    0.87
/data/spleen/image_3    0.91
... ...

The problems are that:

1. I tried to add logic to metrics.update() to cache every record and write to CSV in metrics.complete(), but ignite.metrics only accepts output_transform, so I can’t extract the filenames from engine.state.batch.
2. Then I changed to write a separate handler for this feature, but ignite metrics only saves the final average metrics into engine.state.metrics, handler is not easy to get every metric value corresponding to every image.
3. Another problem is the DistributedDataParallel, when I run the handler in multi-processsing, how do you usually use the multi-processing lock to save content into 1 CSV in both unix and windows OS?

Thanks.

[Nic-Ma]

Hi @vfdev-5 and @sdesrozis ,

Thanks for your discussion. I added self.engine to the metrics in this draft MONAI PR: https://github.com/Project-MONAI/MONAI/pull/1497. Will delete it in the future when you guys added engine to the Metric base class.

Thanks.

[vfdev-5]

@sdesrozis the problem here is that we already have existing API for detach and is_attached method that always require engine and adding Metric.engine would require an update for it too, I think.