Difference MeanIoU vs Jaccard Score

[rot8]

Hey there,

I was wondering why the MeanIoU and BinaryJaccardIndex differ. Shouldn't -by definition- both yield the exact same result?

from torchmetrics.segmentation import MeanIoU
from torchmetrics.classification import BinaryJaccardIndex
import torch
torch.manual_seed(37)
num_classes = 2

preds = torch.randint(0, num_classes, (4, num_classes, 4, 4))
target = torch.randint(0, num_classes, (4, num_classes, 4, 4))


miou = MeanIoU(num_classes=num_classes)
miou_per_class = MeanIoU(num_classes=num_classes, per_class=True, include_background=True)
miou_per_class_no_background = MeanIoU(num_classes=num_classes, per_class=True, include_background=False)
miou(preds, target)
miou_per_class(preds, target)
miou_per_class_no_background(preds, target)

jaccard = BinaryJaccardIndex()
jaccard(preds, target)

• miou = 0.3378
• miou_per_class = [0.4169, 0.2587]
• miou_per_class_no_background = 0.2587
• jaccard = 0.3333

Best, rot8