dmlc--dgl
Tianqi Zhang (张天启)
6999f88f3f
* add random_start option for FPS * change doc * change from random_start to start_idx * change error condition * change error msg Co-authored-by: Minjie Wang <wmjlyjemaine@gmail.com>
59 行
2.0 KiB
Python
59 行
2.0 KiB
Python
"""Farthest Point Sampler for mxnet Geometry package"""
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#pylint: disable=no-member, invalid-name
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from mxnet import nd
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from mxnet.gluon import nn
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import numpy as np
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from ...base import DGLError
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from ..capi import farthest_point_sampler
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class FarthestPointSampler(nn.Block):
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"""Farthest Point Sampler
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In each batch, the algorithm starts with the sample index specified by ``start_idx``.
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Then for each point, we maintain the minimum to-sample distance.
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Finally, we pick the point with the maximum such distance.
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This process will be repeated for ``sample_points`` - 1 times.
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Parameters
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----------
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npoints : int
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The number of points to sample in each batch.
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"""
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def __init__(self, npoints):
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super(FarthestPointSampler, self).__init__()
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self.npoints = npoints
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def forward(self, pos, start_idx=None):
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r"""Memory allocation and sampling
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Parameters
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----------
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pos : tensor
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The positional tensor of shape (B, N, C)
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start_idx : int, optional
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If given, appoint the index of the starting point,
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otherwise randomly select a point as the start point.
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(default: None)
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Returns
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-------
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tensor of shape (B, self.npoints)
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The sampled indices in each batch.
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"""
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ctx = pos.context
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B, N, C = pos.shape
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pos = pos.reshape(-1, C)
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dist = nd.zeros((B * N), dtype=pos.dtype, ctx=ctx)
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if start_idx is None:
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start_idx = nd.random.randint(0, N - 1, (B, ), dtype=np.int, ctx=ctx)
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else:
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if start_idx >= N or start_idx < 0:
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raise DGLError("Invalid start_idx, expected 0 <= start_idx < {}, got {}".format(
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N, start_idx))
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start_idx = nd.full((B, ), start_idx, dtype=np.int, ctx=ctx)
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result = nd.zeros((self.npoints * B), dtype=np.int, ctx=ctx)
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farthest_point_sampler(pos, B, self.npoints, dist, start_idx, result)
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return result.reshape(B, self.npoints)
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