50 lines
1.5 KiB
Python
50 lines
1.5 KiB
Python
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import torch
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import emd_cuda
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class EarthMoverDistanceFunction(torch.autograd.Function):
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@staticmethod
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def forward(ctx, xyz1, xyz2):
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xyz1 = xyz1.contiguous()
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xyz2 = xyz2.contiguous()
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assert xyz1.is_cuda and xyz2.is_cuda, "Only support cuda currently."
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match = emd_cuda.approxmatch_forward(xyz1, xyz2)
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cost = emd_cuda.matchcost_forward(xyz1, xyz2, match)
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ctx.save_for_backward(xyz1, xyz2, match)
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return cost
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@staticmethod
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def backward(ctx, grad_cost):
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xyz1, xyz2, match = ctx.saved_tensors
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grad_cost = grad_cost.contiguous()
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grad_xyz1, grad_xyz2 = emd_cuda.matchcost_backward(grad_cost, xyz1, xyz2, match)
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return grad_xyz1, grad_xyz2
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def earth_mover_distance(xyz1, xyz2, transpose=True):
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"""Earth Mover Distance (Approx)
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Args:
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xyz1 (torch.Tensor): (b, 3, n1)
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xyz2 (torch.Tensor): (b, 3, n1)
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transpose (bool): whether to transpose inputs as it might be BCN format.
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Extensions only support BNC format.
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Returns:
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cost (torch.Tensor): (b)
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"""
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if xyz1.dim() == 2:
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xyz1 = xyz1.unsqueeze(0)
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if xyz2.dim() == 2:
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xyz2 = xyz2.unsqueeze(0)
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if transpose:
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xyz1 = xyz1.transpose(1, 2)
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xyz2 = xyz2.transpose(1, 2)
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# xyz1: B,N,3
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N = xyz1.shape[1]
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assert(xyz1.shape[-1] == 3), f'require it to be B,N,3; get: {xyz1.shape}'
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cost = EarthMoverDistanceFunction.apply(xyz1, xyz2) / float(N)
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return cost
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