Allow conversion of dense to sparse types in SparseTensorType.convert_variable

aesara/sparse/type.py

@@ -4,7 +4,7 @@ import scipy.sparse
 import aesara
 from aesara import scalar as aes
 from aesara.graph.type import HasDataType
-from aesara.tensor.type import TensorType
+from aesara.tensor.type import DenseTensorType, TensorType
 
 
 def _is_sparse(x):
@@ -154,11 +154,25 @@ class SparseTensorType(TensorType, HasDataType):
     def convert_variable(self, var):
         res = super().convert_variable(var)
 
-        if res and not isinstance(res.type, type(self)):
-            # TODO: Convert to this sparse format
-            raise NotImplementedError()
+        if res is None:
+            return res
+
+        if not isinstance(res.type, type(self)):
+            if isinstance(res.type, DenseTensorType):
+                if self.format == "csr":
+                    from aesara.sparse.basic import csr_from_dense
+
+                    return csr_from_dense(res)
+                else:
+                    from aesara.sparse.basic import csc_from_dense
+
+                    return csc_from_dense(res)
+
+            return None
 
+        if res.format != self.format:
             # TODO: Convert sparse `var`s with different formats to this format?
+            return None
 
         return res
 

tests/sparse/test_type.py

-import pytest
-
 from aesara.sparse import matrix as sp_matrix
 from aesara.sparse.type import SparseTensorType
 from aesara.tensor import dmatrix
@@ -16,13 +14,16 @@ def test_Sparse_convert_variable():
     z = sp_matrix("csr", dtype="float64", name="z")
 
     assert y.type.convert_variable(z) is None
+    assert z.type.convert_variable(y) is None
+
+    res = y.type.convert_variable(x)
+    assert res.type == y.type
+
+    res = z.type.convert_variable(x)
+    assert res.type == z.type
 
     # TODO FIXME: This is a questionable result, because `x.type` is associated
     # with a dense `Type`, but, since `TensorType` is a base class of `Sparse`,
     # we would need to added sparse/dense logic to `TensorType`, and we don't
     # want to do that.
     assert x.type.convert_variable(y) is y
-
-    # TODO FIXME: We should be able to do this.
-    with pytest.raises(NotImplementedError):
-        y.type.convert_variable(x)