Accessing diagnostic timers?

[thmiller]

Intro

Hi!

I am a software engineer trying to dig into some Mujoco performance.

My setup

I'm using the Python API installed via pip:

$ pip show mujoco
Name: mujoco
Version: 3.5.0
Summary: MuJoCo Physics Simulator

My question

In https://mujoco.readthedocs.io/en/stable/programming/simulation.html#diagnostics , I saw that Mujoco exposes some timers for parts of the underlying simulation. I'd like to read them, but their durations and "number of calls" fields seem to always be zero. I assume this is because I either installed https://mujoco.readthedocs.io/en/stable/APIreference/APIglobals.html#mjcb-time incorrectly or I'm using the passive viewer incorrectly, but I'm not sure how to fix it.

Minimal model and/or code that explain my question

If you encountered the issue in a complex model, please simplify it as much as possible (while still reproducing the issue).

Model:

minimal XML

<mujoco>
  <worldbody>
    <light pos="0 0 1"/>
    <geom type="sphere" size="1" rgba="1 0 0 1"/>
  </worldbody>
</mujoco>

Code:

import os
import time

import mujoco
import mujoco.viewer


def timer_callback():
    return time.perf_counter() * 1000


def launch(xml: str) -> None:
    mujoco.set_mjcb_time(timer_callback)
    model = mujoco.MjModel.from_xml_path(xml)
    data = mujoco.MjData(model)

    with mujoco.viewer.launch_passive(model, data) as viewer:
        steps = 0
        last_real_time = time.perf_counter()
        last_sim_time = data.time

        while viewer.is_running():
            mujoco.mj_step(model, data)
            viewer.sync()
            steps += 1
            if steps >= 200:
                current_real_time = time.perf_counter()
                current_sim_time = data.time

                real_delta = current_real_time - last_real_time
                sim_delta = current_sim_time - last_sim_time
                if real_delta > 0:
                    rtf = f'{sim_delta / real_delta:6.2f}x'
                else:
                    rtf = 'N/A'
                msg = f"\rSim Time: {current_sim_time:8.2f}s | RTF: {rtf} | "
                timer_string = ' '.join([f"{p[0]}:{p[1].duration}({p[1].number})" for p in zip(mujoco.mjTIMERSTRING, data.timer)])
                msg += f"Timers {timer_string} | "

                print(msg, end="")
                last_real_time = current_real_time
                last_sim_time = current_sim_time
                steps = 0


if __name__ == "__main__":
    launch(os.environ['HOME'] + '/model.xml')

Example output:

Sim Time:   432.80s | RTF: 139.45x | Timers step:0.0(0) forward:0.0(0) inverse:0.0(0) position:0.0(0) velocity:0.0(0) actuation:0.0(0) constraint:0.0(0) advance:0.0(0) pos_kinematics:0.0(0) pos_inertia:0.0(0) pos_collision:0.0(0) pos_make:0.0(0) pos_project:0.0(0) col_broadphase:0.0(0) col_narrowphase:0.0(0) |

Confirmations

• I searched the latest documentation thoroughly before posting.
• I searched previous Issues and Discussions, I am certain this has not been raised before.