fix einsum subscript parsing for specs with spaces

loopy/__init__.py

@@ -532,6 +532,9 @@ def make_einsum(spec, arg_names, **knl_creation_kwargs):
     arg_spec, out_spec = spec.split("->")
     arg_specs = arg_spec.split(",")
 
+    out_spec = out_spec.strip()
+    arg_specs = [arg_spec.strip() for arg_spec in arg_specs]
+
     if len(arg_names) != len(arg_specs):
         raise ValueError(
             f"Number of arg names ({arg_names}) should match the number "

test/test_loopy.py

@@ -3473,6 +3473,16 @@ def test_type_inference_of_clbls_in_substitutions(ctx_factory):
     np.testing.assert_allclose(out.get(), np.abs(10.0*(np.arange(10)-5)))
 
 
+def test_einsum_parsing(ctx_factory):
+    ctx = ctx_factory()
+
+    # See <https://github.com/inducer/loopy/issues/753>
+    knl = lp.make_einsum("ik, kj -> ij", ["A", "B"])
+    knl = lp.add_dtypes(knl, {"A": np.float32, "B": np.float32})
+    lp.auto_test_vs_ref(knl, ctx, knl,
+                        parameters={"Ni": 10, "Nj": 10, "Nk": 10})
+
+
 if __name__ == "__main__":
     if len(sys.argv) > 1:
         exec(sys.argv[1])