Add requested changes

Author: martaiborra

blosc2/__init__.py

@@ -71,6 +71,9 @@ class Tuner(Enum):
     Available tuners.
     """
 
+    #: A 'simple' tuner. This is the default in the Blosc2 library
+    STUNE = 0
+    #: A more sophisticated tuner that can select different codecs/filters for different chunks (more info `here <https://github.com/Blosc/blosc2_btune/>`_).
     BTUNE = 32
 
 

blosc2/core.py

@@ -1230,12 +1230,12 @@ def compute_chunks_blocks(shape, chunks=None, blocks=None, dtype=np.uint8, **kwa
                     cparams2["filters"][i] = blosc2.Filter.NOFILTER
         else:
             cparams2 = cparams
-        # Do not apply specific tuner
+        # Force STUNE to get a hint on the blocksize
         aux_tuner = cparams2["tuner"] if "tuner" in cparams2 else blosc2.Tuner.STUNE
         cparams2["tuner"] = blosc2.Tuner.STUNE
         src = blosc2.compress2(np.zeros(nitems, dtype=f"V{itemsize}"), **cparams2)
-        cparams2["tuner"] = aux_tuner
         _, _, blocksize = blosc2.get_cbuffer_sizes(src)
+        cparams2["tuner"] = aux_tuner
         # Starting point for the guess
         if chunks is None:
             blocks = [1 if shape[i] == 1 else 2 for i in range(len(shape))]

examples/btune.py

@@ -0,0 +1,42 @@
+#######################################################################
+# Copyright (c) 2019-present, Blosc Development Team <[email protected]>
+# All rights reserved.
+#
+# This source code is licensed under a BSD-style license (found in the
+# LICENSE file in the root directory of this source tree)
+#
+# This example can only be run if blosc2-btune is installed. You can
+# get it from https://pypi.org/project/blosc2-btune/
+# For more info on this tuner plugin see
+# https://github.com/Blosc/blosc2_btune/blob/main/README.md
+#######################################################################
+
+import numpy as np
+
+import blosc2
+import blosc2_btune
+
+nchunks = 10
+# Set the compression and decompression parameters, use BTUNE tuner
+cparams = {"codec": blosc2.Codec.LZ4HC, "typesize": 4, "tuner": blosc2.Tuner.BTUNE}
+dparams = {}
+contiguous = True
+urlpath = "filename"
+
+storage = {"contiguous": contiguous, "urlpath": urlpath, "cparams": cparams, "dparams": dparams}
+blosc2.remove_urlpath(urlpath)
+
+# Set the Btune configuration to use
+btune_conf = {"tradeoff": 0.3, "perf_mode": blosc2_btune.PerformanceMode.DECOMP}
+blosc2_btune.set_params_defaults(**kwargs)
+
+# Create the SChunk
+data = np.arange(200 * 1000 * nchunks)
+schunk = blosc2.SChunk(chunksize=200 * 1000 * 4, data=data, **storage)
+
+# Check data can be retrieved correctly
+data2 = np.empty(data.shape, dtype=data.dtype)
+schunk.get_slice(out=data2)
+assert np.array_equal(data, data2)
+
+blosc2.remove_urlpath(urlpath)