Question about obj_scale_loss

[comvee]

Hello, thank you for the nice work!
I have a question about obj_scale_loss.
Why do you use different forms of the scale loss in training and validation phase?
Specifically, in the training phase:

CenterPose/src/lib/trains/object_pose.py

Lines 116 to 117 in 6c89d42

	obj_scale_loss += self.crit_reg(output['scale'], batch['reg_mask'],
	batch['ind'], batch['scale']) / opt.num_stacks

CenterPose/src/lib/models/losses.py

Line 167 in 6c89d42

loss = torch.abs(target * mask - pred * mask).sum(dim=(2, 3))

and in the validation phase:

CenterPose/src/lib/trains/object_pose.py

Lines 126 to 128 in 6c89d42

	# Calculate relative loss only on validation phase
	obj_scale_loss += self.crit_reg(output['scale'], batch['reg_mask'],
	batch['ind'], batch['scale'], relative_loss=True) / opt.num_stacks

CenterPose/src/lib/models/losses.py

Lines 174 to 176 in 6c89d42

	target_rmzero = target.clone()
	target_rmzero[target_rmzero == 0] = 1e-06
	loss = torch.abs((1 * mask - pred * mask) / target_rmzero).sum(dim=(2, 3))

torch.abs(target * mask - pred * mask) and torch.abs((1 * mask - pred * mask) / target_rmzero) does not produce same values.
I want to know the meaning of the "relative loss" in the validation phase and why it is only used in the validation phase.