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Do not fail with zero-sized arrays in dataset_to_point_list #7856

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Merged
merged 1 commit into from
Jul 17, 2025
Merged

Do not fail with zero-sized arrays in dataset_to_point_list #7856

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4 changes: 3 additions & 1 deletion pymc/backends/arviz.py
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Original file line number Diff line number Diff line change
Expand Up @@ -618,11 +618,13 @@ def dataset_to_point_list(
for vn in var_names:
if not isinstance(vn, str):
raise ValueError(f"Variable names must be str, but dataset key {vn} is a {type(vn)}.")

num_sample_dims = len(sample_dims)
stacked_dims = {dim_name: ds[var_names[0]][dim_name] for dim_name in sample_dims}
transposed_dict = {vn: da.transpose(*sample_dims, ...) for vn, da in ds.items()}
stacked_size = np.prod(transposed_dict[var_names[0]].shape[:num_sample_dims], dtype=int)
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should be the same as

stacked_size = np.prod([ds.sizes[dim] for dim in sample_dims], dtype=int)

feel free to choose whichever you prefer

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ds may be a dict

stacked_dict = {
vn: da.values.reshape((-1, *da.shape[num_sample_dims:]))
vn: da.values.reshape((stacked_size, *da.shape[num_sample_dims:]))
for vn, da in transposed_dict.items()
}
points = [
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11 changes: 11 additions & 0 deletions tests/backends/test_arviz.py
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Expand Up @@ -837,3 +837,14 @@ def test_dataset_to_point_list_str_key(self):
ds[3] = xarray.DataArray([1, 2, 3])
with pytest.raises(ValueError, match="must be str"):
dataset_to_point_list(ds, sample_dims=["chain", "draw"])

def test_zero_size(self):
ds = xarray.Dataset()
ds["x"] = xarray.DataArray(
np.zeros((4, 10, 0, 5)), dims=("chain", "draw", "dim_0", "dim_5")
)
pl, _ = dataset_to_point_list(ds, sample_dims=("chain", "draw"))
assert len(pl) == 40
assert tuple(pl[0]) == ("x",)
assert pl[0]["x"].shape == (0, 5)
assert pl[0]["x"].dtype == np.float64