Respect predefined modes in `get_default_mode`

pytensor/compile/__init__.py

@@ -37,7 +37,6 @@ from pytensor.compile.mode import (
     PrintCurrentFunctionGraph,
     get_default_mode,
     get_mode,
-    instantiated_default_mode,
     local_useless,
     optdb,
     predefined_linkers,

pytensor/compile/mode.py

@@ -492,7 +492,7 @@ predefined_modes = {
     "PYTORCH": PYTORCH,
 }
 
-instantiated_default_mode = None
+_CACHED_RUNTIME_MODES: dict[str, Mode] = {}
 
 
 def get_mode(orig_string):
@@ -500,50 +500,46 @@ def get_mode(orig_string):
         string = config.mode
     else:
         string = orig_string
+
     if not isinstance(string, str):
         return string  # it is hopefully already a mode...
 
-    global instantiated_default_mode
-    # The default mode is cached. However, config.mode can change
-    # If instantiated_default_mode has the right class, use it.
-    if orig_string is None and instantiated_default_mode:
-        if string in predefined_modes:
-            default_mode_class = predefined_modes[string].__class__.__name__
-        else:
-            default_mode_class = string
-        if instantiated_default_mode.__class__.__name__ == default_mode_class:
-            return instantiated_default_mode
-
-    if string in ("Mode", "DebugMode", "NanGuardMode"):
-        if string == "DebugMode":
-            # need to import later to break circular dependency.
-            from .debugmode import DebugMode
-
-            # DebugMode use its own linker.
-            ret = DebugMode(optimizer=config.optimizer)
-        elif string == "NanGuardMode":
-            # need to import later to break circular dependency.
-            from .nanguardmode import NanGuardMode
-
-            # NanGuardMode use its own linker.
-            ret = NanGuardMode(True, True, True, optimizer=config.optimizer)
-        else:
-            # TODO: Can't we look up the name and invoke it rather than using eval here?
-            ret = eval(string + "(linker=config.linker, optimizer=config.optimizer)")
-    elif string in predefined_modes:
-        ret = predefined_modes[string]
-    else:
-        raise Exception(f"No predefined mode exist for string: {string}")
+    # Keep the original string for error messages
+    upper_string = string.upper()
 
-    if orig_string is None:
-        # Build and cache the default mode
-        if config.optimizer_excluding:
-            ret = ret.excluding(*config.optimizer_excluding.split(":"))
-        if config.optimizer_including:
-            ret = ret.including(*config.optimizer_including.split(":"))
-        if config.optimizer_requiring:
-            ret = ret.requiring(*config.optimizer_requiring.split(":"))
-        instantiated_default_mode = ret
+    if upper_string in predefined_modes:
+        return predefined_modes[upper_string]
+
+    global _CACHED_RUNTIME_MODES
+
+    if upper_string in _CACHED_RUNTIME_MODES:
+        return _CACHED_RUNTIME_MODES[upper_string]
+
+    # Need to define the mode for the first time
+    if upper_string == "MODE":
+        ret = Mode(linker=config.linker, optimizer=config.optimizer)
+    elif upper_string in ("DEBUGMODE", "DEBUG_MODE"):
+        from pytensor.compile.debugmode import DebugMode
+
+        # DebugMode use its own linker.
+        ret = DebugMode(optimizer=config.optimizer)
+    elif upper_string == "NANGUARDMODE":
+        from pytensor.compile.nanguardmode import NanGuardMode
+
+        # NanGuardMode use its own linker.
+        ret = NanGuardMode(True, True, True, optimizer=config.optimizer)
+
+    else:
+        raise ValueError(f"No predefined mode exist for string: {string}")
+
+    if config.optimizer_excluding:
+        ret = ret.excluding(*config.optimizer_excluding.split(":"))
+    if config.optimizer_including:
+        ret = ret.including(*config.optimizer_including.split(":"))
+    if config.optimizer_requiring:
+        ret = ret.requiring(*config.optimizer_requiring.split(":"))
+    # Cache the mode for next time
+    _CACHED_RUNTIME_MODES[upper_string] = ret
 
     return ret
 

pytensor/configdefaults.py

@@ -387,7 +387,8 @@ def add_compile_configvars():
     config.add(
         "linker",
         "Default linker used if the pytensor flags mode is Mode",
-        EnumStr("cvm", linker_options),
+        # Not mutable because the default mode is cached after the first use.
+        EnumStr("cvm", linker_options, mutable=False),
         in_c_key=False,
     )
 
@@ -410,6 +411,7 @@ def add_compile_configvars():
         EnumStr(
             "o4",
             ["o3", "o2", "o1", "unsafe", "fast_run", "fast_compile", "merge", "None"],
+            mutable=False,  # Not mutable because the default mode is cached after the first use.
         ),
         in_c_key=False,
     )

tests/compile/function/test_types.py

@@ -1105,14 +1105,10 @@ class TestPicklefunction:
             ((a.T.T) * (dot(xm, (sm.T.T.T)) + x).T * (x / x) + s),
         )
         old_default_mode = config.mode
-        old_default_opt = config.optimizer
-        old_default_link = config.linker
         try:
             try:
                 str_f = pickle.dumps(f, protocol=-1)
-                config.mode = "Mode"
-                config.linker = "py"
-                config.optimizer = "None"
+                config.mode = "NUMBA"
                 g = pickle.loads(str_f)
                 # print g.maker.mode
                 # print compile.mode.default_mode
@@ -1121,8 +1117,6 @@ class TestPicklefunction:
                     g = "ok"
         finally:
             config.mode = old_default_mode
-            config.optimizer = old_default_opt
-            config.linker = old_default_link
 
         if g == "ok":
             return

tests/compile/test_mode.py

@@ -13,6 +13,7 @@ from pytensor.configdefaults import config
 from pytensor.graph.features import NoOutputFromInplace
 from pytensor.graph.rewriting.db import RewriteDatabaseQuery, SequenceDB
 from pytensor.link.basic import LocalLinker
+from pytensor.link.jax import JAXLinker
 from pytensor.tensor.math import dot, tanh
 from pytensor.tensor.type import matrix, vector
 
@@ -142,3 +143,15 @@ def test_get_target_language():
     test_mode = Mode(linker=MyLinker())
     with pytest.raises(Exception):
         get_target_language(test_mode)
+
+
+def test_predefined_modes_respected():
+    default_mode = get_default_mode()
+    assert not isinstance(default_mode.linker, JAXLinker)
+
+    with config.change_flags(mode="JAX"):
+        jax_mode = get_default_mode()
+        assert isinstance(jax_mode.linker, JAXLinker)
+
+    default_mode_again = get_default_mode()
+    assert not isinstance(default_mode_again.linker, JAXLinker)