Re-fix scalar parallel reductions

loopy/preprocess.py

@@ -455,6 +455,12 @@ def realize_reduction(kernel, insn_id_filter=None, unknown_types_ok=True):
                 depends_on=frozenset())
         generated_insns.append(init_insn)
 
+        def _strip_if_scalar(c):
+            if len(acc_vars) == 1:
+                return c[0]
+            else:
+                return c
+
         init_neutral_id = insn_id_gen("%s_%s_init_neutral" % (insn.id, red_iname))
         init_neutral_insn = make_assignment(
                 id=init_neutral_id,
@@ -473,7 +479,7 @@ def realize_reduction(kernel, insn_id_filter=None, unknown_types_ok=True):
                     for acc_var in acc_vars),
                 expression=expr.operation(
                     arg_dtype,
-                    tuple(var(nvn) for nvn in neutral_var_names),
+                    _strip_if_scalar(tuple(var(nvn) for nvn in neutral_var_names)),
                     expr.expr, expr.inames),
                 within_inames=(
                     (outer_insn_inames - frozenset(expr.inames))
@@ -483,12 +489,6 @@ def realize_reduction(kernel, insn_id_filter=None, unknown_types_ok=True):
                 no_sync_with=frozenset([(init_id, "any")]))
         generated_insns.append(transfer_insn)
 
-        def _strip_if_scalar(c):
-            if len(acc_vars) == 1:
-                return c[0]
-            else:
-                return c
-
         cur_size = 1
         while cur_size < size:
             cur_size *= 2