Remove fine-grained timing from narrow-phase collision functions, delete mjTIMER_COL_MID.

PiperOrigin-RevId: 599225419
Change-Id: Ieca166753c20a0abf660e2821b2844dda8758951

doc/changelog.rst

@@ -9,17 +9,20 @@ General
 ^^^^^^^
 1. Improved the :ref:discardvisual<compiler-discardvisual> compiler flag, which now discards all visual-only assets. See
    :ref:discardvisual<compiler-discardvisual> for details.
+2. Removed the :ref:`timer<mjtTimer>` for midphase colllision detection, it is now folded in with the narrowphase
+   timer. This is because timing the two phases seperately required fine-grained timers inside the collision
+   functions; these functions are so small and fast that the timer itself was incurring a measurable cost.
 
 MJX
 ^^^
-2. Added :ref:`dyntype<actuator-general-dyntype>` ``filterexact``.
-3. Added :at:`site` transmission.
-4. Updated MJX colab tutorial with more stable quadruped environment.
-5. Added ``mjx.ray`` which mirrors :ref:`mj_ray` for planes, spheres, capsules, boxes, and meshes.
+3. Added :ref:`dyntype<actuator-general-dyntype>` ``filterexact``.
+4. Added :at:`site` transmission.
+5. Updated MJX colab tutorial with more stable quadruped environment.
+6. Added ``mjx.ray`` which mirrors :ref:`mj_ray` for planes, spheres, capsules, boxes, and meshes.
 
 Bug fixes
 ^^^^^^^^^
-6. Fixed a bug that prevented the use of pins with plugins if flexes are not in the worldbody. Fixes
+7. Fixed a bug that prevented the use of pins with plugins if flexes are not in the worldbody. Fixes
    :github:issue:`1270`.
 7. Fixed a bug in the :ref:`muscle model<CMuscle>` that led to non-zero values outside the lower
    bound of the length range. Fixes :github:issue:`1342`.

doc/includes/references.h

@@ -75,7 +75,6 @@ typedef enum mjtTimer_ {     // internal timers
 
   // breakdown of mj_collision
   mjTIMER_COL_BROAD,         // broadphase
-  mjTIMER_COL_MID,           // midphase
   mjTIMER_COL_NARROW,        // narrowphase
 
   mjNTIMER                   // number of timers