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Fix SZ and SZ3 from_filter_options for chunks with 3 or more dimensions #412

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Fix SZ and SZ3 from_filter_options for chunks with 3 or more dimensions #412

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15 changes: 15 additions & 0 deletions src/hdf5plugin/_filters.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1089,6 +1089,19 @@ def _sz_unpack_float64(high: int, low: int) -> float:
return float(struct.unpack(">d", packed)[0])


def _sz_strip_dims(filter_options: tuple[int, ...]) -> tuple[int, ...]:
"""Returns SZ/SZ3 "cd_values" without the leading chunk shape information

The filter stores (ndim, dtype, dims...) first:
4 values for 1 and 2 dimensions, ndim + 2 values otherwise.
See SZ_cdArrayToMetaDataErr in H5Z_SZ.c and H5Z_SZ3.cpp.
"""
ndim = filter_options[0] if filter_options else 0
offset = 4 if ndim <= 2 else ndim + 2
# Keep 4 leading values so indices match the 1D/2D layout
return (*filter_options[:4], *filter_options[offset:])


class SZ(FilterBase):
"""``h5py.Group.create_dataset``'s compression arguments for using SZ2 filter.

Expand Down Expand Up @@ -1185,6 +1198,7 @@ def _from_filter_options(cls, filter_options: tuple[int, ...]) -> SZ:
(_, _, _, _, mode, absolute1, absolute2, relative1, relative2, pointwise1, pointwise2)
:raises ValueError: Unsupported filter_options
"""
filter_options = _sz_strip_dims(filter_options)
if len(filter_options) < 13:
raise ValueError(f"Expected 13 values, got {len(filter_options)}")

Expand Down Expand Up @@ -1286,6 +1300,7 @@ def _from_filter_options(cls, filter_options: tuple[int, ...]) -> SZ3:
(_, _, _, _, mode, absolute1, absolute2, relative1, relative2, norm2_1, norm2_2, pointwise1, pointwise2)
:raises ValueError: Unsupported filter_options
"""
filter_options = _sz_strip_dims(filter_options)
if len(filter_options) < 13:
raise ValueError(f"Expected 13 values, got {len(filter_options)}")

Expand Down
20 changes: 20 additions & 0 deletions src/hdf5plugin/test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -658,6 +658,18 @@ def testSZ(self):
(1, 0, 0, 256, 10, 0, 0, 0, 0, 1062232653, 3539053052, 0, 0),
hdf5plugin.SZ(pointwise_relative=1e-3),
),
( # 2D chunk
(2, 0, 32, 32, 0, 1062232653, 3539053052, 0, 0, 0, 0, 0, 0),
hdf5plugin.SZ(absolute=1e-3),
),
( # 3D chunk
(3, 0, 32, 32, 4, 0, 1062232653, 3539053052, 0, 0, 0, 0, 0, 0),
hdf5plugin.SZ(absolute=1e-3),
),
( # 4D chunk
(4, 0, 16, 16, 2, 2, 1, 0, 0, 1062232653, 3539053052, 0, 0, 0, 0),
hdf5plugin.SZ(relative=1e-3),
),
):
with self.subTest(filter_options=filter_options):
compression_filter = hdf5plugin.SZ._from_filter_options(filter_options)
Expand Down Expand Up @@ -687,6 +699,14 @@ def testSZ3(self):
(1, 0, 0, 256, 3, 0, 0, 0, 0, 0, 0, 1062232653, 3539053052),
hdf5plugin.SZ3(peak_signal_to_noise_ratio=1e-3),
),
( # 3D chunk
(3, 0, 32, 32, 4, 0, 1062232653, 3539053052, 0, 0, 0, 0, 0, 0),
hdf5plugin.SZ3(absolute=1e-3),
),
( # 4D chunk
(4, 0, 16, 16, 2, 2, 2, 0, 0, 0, 0, 1062232653, 3539053052, 0, 0),
hdf5plugin.SZ3(norm2=1e-3),
),
):
with self.subTest(filter_options=filter_options):
compression_filter = hdf5plugin.SZ3._from_filter_options(filter_options)
Expand Down