Minimal changes for enabling miniexpr for windows

Author: FrancescAlted

RELEASE_NOTES.md

@@ -2,7 +2,8 @@
 
 ## Changes from 4.0.0-b1 to 4.0.0-b2
 
-XXX version-specific blurb XXX
+- On Windows, miniexpr is temporarily disabled for integral outputs and mixed-dtype expressions.
+  Set `BLOSC2_ENABLE_MINIEXPR_WINDOWS=1` to override this for testing.
 
 ## Changes from 3.12.2 to 4.0.0-b1
 

src/blosc2/blosc2_ext.pyx

@@ -1947,6 +1947,7 @@ cdef int aux_miniexpr(me_udata *udata, int64_t nchunk, int32_t nblock,
             memset(params_output, 0, udata.array.blocknitems * typesize)
         free(input_buffers)
         return 0
+
     for i in range(udata.ninputs):
         ndarr = udata.inputs[i]
         input_buffers[i] = malloc(ndarr.sc.blocksize)
@@ -2013,14 +2014,19 @@ cdef int aux_miniexpr(me_udata *udata, int64_t nchunk, int32_t nblock,
     cdef uintptr_t offset_bytes = typesize * linear_block_index
 
     # Call thread-safe miniexpr C API
+    # NOTE: me_eval_nd expects the OUTPUT block size (in items), not the input block size.
+    # For element-wise operations with same dtypes, they're equal, but for type-changing
+    # operations (e.g., arccos(int32) -> float64), we must use the output's block item count.
+    cdef int output_blocknitems = udata.array.blocknitems
+
     if udata.aux_reduc_ptr == NULL:
         aux_reduc_ptr = <void *> params_output
     else:
         # Reduction operation: evaluate only valid items into a single output element.
         # NOTE: miniexpr handles scalar outputs in me_eval_nd without touching tail bytes.
         aux_reduc_ptr = <void *> (<uintptr_t> udata.aux_reduc_ptr + offset_bytes)
     rc = me_eval_nd(miniexpr_handle, <const void**> input_buffers, udata.ninputs,
-                    aux_reduc_ptr, blocknitems, nchunk, nblock, udata.eval_params)
+                    aux_reduc_ptr, output_blocknitems, nchunk, nblock, udata.eval_params)
     if rc != 0:
         raise RuntimeError(f"miniexpr: issues during evaluation; error code: {rc}")
 

src/blosc2/lazyexpr.py

@@ -95,10 +95,9 @@
 try_miniexpr = True
 if blosc2.IS_WASM:
     try_miniexpr = False
-if sys.platform == "win32":
-    # Although miniexpr has support for windows, the integration with Blosc2
-    # still has some rough edges.
-    try_miniexpr = False
+
+_MINIEXPR_WINDOWS_OVERRIDE = os.environ.get("BLOSC2_ENABLE_MINIEXPR_WINDOWS", "").strip().lower()
+_MINIEXPR_WINDOWS_OVERRIDE = _MINIEXPR_WINDOWS_OVERRIDE not in ("", "0", "false", "no", "off")
 
 
 def ne_evaluate(expression, local_dict=None, **kwargs):
@@ -1326,6 +1325,26 @@ def fast_eval(  # noqa: C901
             use_miniexpr = False
         if not (all_ndarray and out is None):
             use_miniexpr = False
+        has_complex = any(
+            isinstance(op, blosc2.NDArray) and blosc2.isdtype(op.dtype, "complex floating")
+            for op in operands.values()
+        )
+        if isinstance(expression, str) and has_complex:
+            if sys.platform == "win32":
+                # On Windows, miniexpr has issues with complex numbers
+                use_miniexpr = False
+            if any(tok in expression for tok in ("!=", "==", "<=", ">=", "<", ">")):
+                use_miniexpr = False
+        if sys.platform == "win32" and use_miniexpr and not _MINIEXPR_WINDOWS_OVERRIDE:
+            # Work around Windows miniexpr issues for integer outputs and dtype conversions.
+            if blosc2.isdtype(dtype, "integral"):
+                use_miniexpr = False
+            else:
+                dtype_mismatch = any(
+                    isinstance(op, blosc2.NDArray) and op.dtype != dtype for op in operands.values()
+                )
+                if dtype_mismatch:
+                    use_miniexpr = False
 
     if use_miniexpr:
         cparams = kwargs.pop("cparams", blosc2.CParams())
@@ -2036,6 +2055,18 @@ def reduce_slices(  # noqa: C901
             isinstance(op, blosc2.NDArray) and blosc2.isdtype(op.dtype, "complex floating")
             for op in operands.values()
         )
+        if has_complex and sys.platform == "win32":
+            # On Windows, miniexpr has issues with complex numbers
+            use_miniexpr = False
+        if sys.platform == "win32" and use_miniexpr and not _MINIEXPR_WINDOWS_OVERRIDE:
+            if blosc2.isdtype(dtype, "integral"):
+                use_miniexpr = False
+            else:
+                dtype_mismatch = any(
+                    isinstance(op, blosc2.NDArray) and op.dtype != dtype for op in operands.values()
+                )
+                if dtype_mismatch:
+                    use_miniexpr = False
         if has_complex and any(tok in expression for tok in ("!=", "==", "<=", ">=", "<", ">")):
             use_miniexpr = False
         if where is not None and len(where) != 2: