SurfaceDistanceMetric (SDM) and HausdorffDistanceMetric (HDM) print wrong all-zero warning messages #2627
Description
Describe the bug
SDM and HDM incorrectly warn that both prediction and ground truth are all 0 (for some class) even when only one of them is all 0 (for some class):
To Reproduce
Steps to reproduce the behavior (for HDM):
import torch
import monai
metric = monai.metrics.HausdorffDistanceMetric()
#forward direction
metric(torch.cat((torch.ones(1,1,256,256),torch.zeros(1,1,256,256)), dim=1), torch.randint(0,2,(1,2,256,256)))
/autofs/space/vault_021/users/siy0/anaconda3/lib/python3.8/site-packages/monai/metrics/utils.py:199: UserWarning: prediction is all 0, this may result in nan/inf distance.
warnings.warn("prediction is all 0, this may result in nan/inf distance.")
/autofs/space/vault_021/users/siy0/anaconda3/lib/python3.8/site-packages/monai/metrics/utils.py:195: UserWarning: ground truth is all 0, this may result in nan/inf distance.
warnings.warn("ground truth is all 0, this may result in nan/inf distance.")
#backward direction
metric(torch.randint(0,2,(1,2,256,256)),torch.cat((torch.ones(1,1,256,256),torch.zeros(1,1,256,256)), dim=1))
/autofs/space/vault_021/users/siy0/anaconda3/lib/python3.8/site-packages/monai/metrics/utils.py:195: UserWarning: ground truth is all 0, this may result in nan/inf distance.
warnings.warn("ground truth is all 0, this may result in nan/inf distance.")
/autofs/space/vault_021/users/siy0/anaconda3/lib/python3.8/site-packages/monai/metrics/utils.py:199: UserWarning: prediction is all 0, this may result in nan/inf distance.
warnings.warn("prediction is all 0, this may result in nan/inf distance.")
The same bug is there if SDM is run with symmetric=True
Expected behavior
Only the first warning should be displayed in each of the two above cases.