150 lines
4.1 KiB
Python
150 lines
4.1 KiB
Python
import torch
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import matplotlib
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def get_random_messages(count, order):
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"""
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Generate a list of messages.
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:param count: Number of messages to generate.
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:param order: Number of possible messages.
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:return: One-dimensional vector with each entry being the index of the
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generated message which is between 0, inclusive, and `order`, exclusive.
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>>> get_random_messages(5)
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torch.tensor([0, 2, 0, 3, 4])
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"""
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return torch.randint(0, order, (count,))
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def messages_to_onehot(messages, order):
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"""
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Convert messages represented as indexes to one-hot encoding.
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:param messages: List of messages to convert.
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:param order: Number of possible messages.
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:return: One-hot encoded messages.
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>>> messages_to_onehot(torch.tensor([0, 2, 0, 3, 4]))
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torch.tensor([
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[1., 0., 0., 0., 0.],
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[0., 0., 1., 0., 0.],
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[1., 0., 0., 0., 0.],
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[0., 0., 0., 1., 0.],
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[0., 0., 0., 0., 1.],
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])
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"""
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return torch.nn.functional.one_hot(messages, num_classes=order).float()
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def plot_constellation(
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ax,
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constellation,
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channel,
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decoder,
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grid_step=0.05,
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noise_samples=1000
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):
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"""
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Plot a constellation with its decoder and channel noise.
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:param ax: Matplotlib axes to plot on.
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:param constellation: Constellation to plot.
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:param channel: Channel model to use for generating noise.
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:param decoder: Decoder function able to map the constellation points back
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to the original messages.
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:param grid_step: Grid step used for drawing the decision regions,
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expressed as percentage of the total plot width (or equivalently height).
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Lower steps makes more precise grids but takes more time to compute.
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:param noise_samples: Number of noisy points to sample and plot.
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"""
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ax.grid()
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order = len(constellation)
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color_map = matplotlib.cm.Dark2
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color_norm = matplotlib.colors.BoundaryNorm(range(order + 1), order)
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# Extend axes symmetrically around zero so that they fit data
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axis_extent = max(
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abs(constellation.min()),
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abs(constellation.max())
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) * 1.05
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ax.set_xlim(-axis_extent, axis_extent)
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ax.set_ylim(-axis_extent, axis_extent)
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# Hide borders but keep ticks
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for direction in ['left', 'bottom', 'right', 'top']:
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ax.axis[direction].line.set_color('#00000000')
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# Show zero-centered axes without ticks
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for direction in ['xzero', 'yzero']:
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axis = ax.axis[direction]
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axis.set_visible(True)
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axis.set_axisline_style('-|>')
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axis.major_ticklabels.set_visible(False)
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# Add axis names
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ax.annotate(
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'I', (1, 0.5), xycoords='axes fraction',
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xytext=(25, 0), textcoords='offset points',
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va='center', ha='right'
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)
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ax.annotate(
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'Q', (0.5, 1), xycoords='axes fraction',
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xytext=(0, 25), textcoords='offset points',
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va='center', ha='center'
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)
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# Plot decision regions
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regions_extent = 2 * axis_extent
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step = grid_step * regions_extent
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grid_range = torch.arange(-regions_extent, regions_extent, step)
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grid_y, grid_x = torch.meshgrid(grid_range, grid_range)
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grid_images = decoder(torch.stack((grid_x, grid_y), dim=2)).argmax(dim=2)
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ax.imshow(
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grid_images,
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extent=(
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-regions_extent, regions_extent,
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-regions_extent, regions_extent
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),
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aspect='auto',
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origin='lower',
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cmap=color_map,
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norm=color_norm,
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alpha=0.2
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)
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# Plot constellation
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ax.scatter(
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*zip(*constellation.tolist()),
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zorder=10,
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s=60,
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c=range(order),
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edgecolor='black',
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cmap=color_map,
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norm=color_norm,
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)
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# Plot constellation center
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center = constellation.sum(dim=0) / order
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ax.scatter(
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center[0], center[1],
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marker='X',
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)
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# Plot channel noise
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noisy_vectors = channel(constellation.repeat(noise_samples, 1))
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ax.scatter(
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*zip(*noisy_vectors.tolist()),
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marker='.',
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s=5,
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c=list(range(order)) * noise_samples,
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cmap=color_map,
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norm=color_norm,
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alpha=0.7,
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zorder=8
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)
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