78 lines
3 KiB
Python
78 lines
3 KiB
Python
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# Copyright (c) 2021, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
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#
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# NVIDIA CORPORATION and its licensors retain all intellectual property
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# and proprietary rights in and to this software, related documentation
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# and any modifications thereto. Any use, reproduction, disclosure or
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# distribution of this software and related documentation without an express
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# license agreement from NVIDIA CORPORATION is strictly prohibited.
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"""Custom replacement for `torch.nn.functional.grid_sample` that
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supports arbitrarily high order gradients between the input and output.
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Only works on 2D images and assumes
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`mode='bilinear'`, `padding_mode='zeros'`, `align_corners=False`."""
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import torch
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# pylint: disable=redefined-builtin
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# pylint: disable=arguments-differ
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# pylint: disable=protected-access
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#----------------------------------------------------------------------------
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enabled = False # Enable the custom op by setting this to true.
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#----------------------------------------------------------------------------
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def grid_sample(input, grid):
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if _should_use_custom_op():
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return _GridSample2dForward.apply(input, grid)
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return torch.nn.functional.grid_sample(input=input, grid=grid, mode='bilinear', padding_mode='zeros', align_corners=False)
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#----------------------------------------------------------------------------
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def _should_use_custom_op():
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return enabled
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#----------------------------------------------------------------------------
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class _GridSample2dForward(torch.autograd.Function):
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@staticmethod
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def forward(ctx, input, grid):
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assert input.ndim == 4
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assert grid.ndim == 4
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output = torch.nn.functional.grid_sample(input=input, grid=grid, mode='bilinear', padding_mode='zeros', align_corners=False)
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ctx.save_for_backward(input, grid)
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return output
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@staticmethod
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def backward(ctx, grad_output):
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input, grid = ctx.saved_tensors
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grad_input, grad_grid = _GridSample2dBackward.apply(grad_output, input, grid)
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return grad_input, grad_grid
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#----------------------------------------------------------------------------
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class _GridSample2dBackward(torch.autograd.Function):
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@staticmethod
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def forward(ctx, grad_output, input, grid):
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op = torch._C._jit_get_operation('aten::grid_sampler_2d_backward')
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grad_input, grad_grid = op(grad_output, input, grid, 0, 0, False)
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ctx.save_for_backward(grid)
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return grad_input, grad_grid
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@staticmethod
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def backward(ctx, grad2_grad_input, grad2_grad_grid):
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_ = grad2_grad_grid # unused
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grid, = ctx.saved_tensors
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grad2_grad_output = None
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grad2_input = None
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grad2_grid = None
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if ctx.needs_input_grad[0]:
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grad2_grad_output = _GridSample2dForward.apply(grad2_grad_input, grid)
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assert not ctx.needs_input_grad[2]
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return grad2_grad_output, grad2_input, grad2_grid
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#----------------------------------------------------------------------------
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