ops_ext to replace cpu import (#3409)

* ops_ext to replace cpu import

* don't allow zero copy with as buffer

* memoryview(bytearray

* reenable test

* fix jit issue

test/external/external_test_example.py

@@ -7,7 +7,7 @@ def multidevice_test(fxn):
   exclude_devices = getenv("EXCLUDE_DEVICES", "").split(",")
   def ret(self):
     for device in Device._devices:
-      if device in ["DISK", "FAKE"]: continue
+      if device in ["DISK", "EXT", "FAKE"]: continue
       if not CI: print(device)
       if device in exclude_devices:
         if not CI: print(f"WARNING: {device} test is excluded")

test/test_schedule.py

@@ -350,7 +350,7 @@ class TestSchedule(unittest.TestCase):
 
   def test_double_from(self):
     x = Tensor([1,2,3,4])
-    out = x.to('cpu')
+    out = x.to('ext')
     check_schedule(out, 0, filter_loadops=False)
 
   def test_pow_const_tensor_simplified(self):