Refactor thread pool implementation.

- Make mjTask non-opaque and remove C++ Task class.
- Make C++ thread pool a subclass of a skeletal mjThreadPool C struct.
- Make the mjTask status enum more consistent with the rest of MuJoCo.
- Change mju_threadPoolEnqueue to take just the mjTask. Users must now prepare the mjTask by assigning the function pointer and argument into the struct.
- Rename files in thread/ to be more consistent with the rest of MuJoCo.
- Run threading tests in CMake.
- Allow use of C++20 designated initializers.

Otherwise the functionality remains identical.

PiperOrigin-RevId: 564374675
Change-Id: I37c9894566bc39faf217e5aa97a4e2713a70e467

introspect/codegen/generate_enums.py

@@ -56,7 +56,10 @@ class MjEnumVisitor:
       child_kind = child.get('kind')
       if child_kind == 'EnumConstantDecl':
         next_idx = values[-1][1] + 1 if values else 0
-        value = int(child['inner'][0].get('value', next_idx))
+        if 'inner' in child:
+          value = int(child['inner'][0].get('value', next_idx))
+        else:
+          value = next_idx
         values.append((child['name'], value))
     return ast_nodes.EnumDecl(name=name, declname=name, values=dict(values))
 

introspect/enums.py

@@ -642,6 +642,16 @@ ENUMS: Mapping[str, EnumDecl] = dict([
              ('mjFONT_BIG', 2),
          ]),
      )),
+    ('mjtTaskStatus',
+     EnumDecl(
+         name='mjtTaskStatus',
+         declname='enum mjtTaskStatus_',
+         values=dict([
+             ('mjTASK_NEW', 0),
+             ('mjTASK_QUEUED', 1),
+             ('mjTASK_COMPLETED', 2),
+         ]),
+     )),
     ('mjtButton',
      EnumDecl(
          name='mjtButton',

introspect/functions.py

@@ -8269,7 +8269,7 @@ FUNCTIONS: Mapping[str, FunctionDecl] = dict([
                  type=ValueType(name='size_t'),
              ),
          ),
-         doc='Creates a thread pool with the specified number of threads running.',  # pylint: disable=line-too-long
+         doc='Create a thread pool with the specified number of threads running.',  # pylint: disable=line-too-long
      )),
     ('mju_threadPoolEnqueue',
      FunctionDecl(
@@ -8288,32 +8288,8 @@ FUNCTIONS: Mapping[str, FunctionDecl] = dict([
                      inner_type=ValueType(name='mjTask'),
                  ),
              ),
-             FunctionParameterDecl(
-                 name='start_routine',
-                 type=ValueType(name='void *(*)(void *)'),
-             ),
-             FunctionParameterDecl(
-                 name='args',
-                 type=PointerType(
-                     inner_type=ValueType(name='void'),
-                 ),
-             ),
          ),
-         doc='Enqueues a task in a thread pool.',
-     )),
-    ('mju_taskJoin',
-     FunctionDecl(
-         name='mju_taskJoin',
-         return_type=ValueType(name='void'),
-         parameters=(
-             FunctionParameterDecl(
-                 name='task',
-                 type=PointerType(
-                     inner_type=ValueType(name='mjTask'),
-                 ),
-             ),
-         ),
-         doc='Waits for a task to complete.',
+         doc='Enqueue a task in a thread pool.',
      )),
     ('mju_threadPoolDestroy',
      FunctionDecl(
@@ -8327,6 +8303,34 @@ FUNCTIONS: Mapping[str, FunctionDecl] = dict([
                  ),
              ),
          ),
-         doc='Destroys a thread pool.',
+         doc='Destroy a thread pool.',
+     )),
+    ('mju_defaultTask',
+     FunctionDecl(
+         name='mju_defaultTask',
+         return_type=ValueType(name='void'),
+         parameters=(
+             FunctionParameterDecl(
+                 name='task',
+                 type=PointerType(
+                     inner_type=ValueType(name='mjTask'),
+                 ),
+             ),
+         ),
+         doc='Initialize an mjTask.',
+     )),
+    ('mju_taskJoin',
+     FunctionDecl(
+         name='mju_taskJoin',
+         return_type=ValueType(name='void'),
+         parameters=(
+             FunctionParameterDecl(
+                 name='task',
+                 type=PointerType(
+                     inner_type=ValueType(name='mjTask'),
+                 ),
+             ),
+         ),
+         doc='Wait for a task to complete.',
      )),
 ])

introspect/structs.py

@@ -7007,33 +7007,39 @@ STRUCTS: Mapping[str, StructDecl] = dict([
              ),
          ),
      )),
-    ('mjTask',
-     StructDecl(
-         name='mjTask',
-         declname='struct mjTask_',
-         fields=(
-             StructFieldDecl(
-                 name='buffer',
-                 type=ArrayType(
-                     inner_type=ValueType(name='char'),
-                     extents=(24,),
-                 ),
-                 doc='',
-             ),
-         ),
-     )),
     ('mjThreadPool',
      StructDecl(
          name='mjThreadPool',
          declname='struct mjThreadPool_',
          fields=(
              StructFieldDecl(
-                 name='buffer',
-                 type=ArrayType(
-                     inner_type=ValueType(name='char'),
-                     extents=(6208,),
+                 name='nworker',
+                 type=ValueType(name='int'),
+                 doc='number of workers in the pool',
+             ),
+         ),
+     )),
+    ('mjTask',
+     StructDecl(
+         name='mjTask',
+         declname='struct mjTask_',
+         fields=(
+             StructFieldDecl(
+                 name='func',
+                 type=ValueType(name='mjfTask'),
+                 doc='pointer to the function that implements the task',
+             ),
+             StructFieldDecl(
+                 name='args',
+                 type=PointerType(
+                     inner_type=ValueType(name='void'),
                  ),
-                 doc='',
+                 doc='arguments to func',
+             ),
+             StructFieldDecl(
+                 name='status',
+                 type=ValueType(name='int', is_volatile=True),
+                 doc='status of the task',
              ),
          ),
      )),