[linux-64] MPPI 1.3.12 predicts motion in the wrong direction due to stale build dependency (xsimd / fast-math)

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Issue

On Ubuntu 24.04 / ROS 2 Jazzy, the apt-distributed MPPI generates forward commands, while the RoboStack build generates predominantly reverse commands despite the global path being ahead. Both were tested on the same machine with the same Nav2 version, controller configuration, and recorded inputs.

(The apt binary's exact build dependencies have not been verified. RoboStack build dependencies were read from the affected artifact's info/recipe/rendered_recipe.yaml.)

Investigation

The error appears in MPPI's batch trajectory integration, before critic scoring. The Nav2 1.3.12 integrator uses SIMD sine/cosine to convert sampled velocities into candidate positions. Its CMake configuration enables xsimd and -ffast-math.

A standalone test using the same xsimd 10.0.0 headers as the RoboStack build produces incorrect signs:

The suspected cause is the interaction between fast-math and xsimd's use of positive/negative zero as sign masks. Removing -ffast-math or appending -fsigned-zeros restores the expected numerical results.

The installed MPPI integrator also predicts −0.270 m along X instead of +0.280 m for a straight trajectory at yaw=0, vx=0.1 m/s, and 56 steps of 0.05 s. Incorrect candidate directions can therefore make a reverse command appear to approach the forward path.

Would updating the build-time xsimd dependency and rebuilding MPPI possible? A newer xsimd alone is not yet a confirmed fix; if errors persist, disabling -ffast-math may be necessary.

Installed packages

ros2-nav2-mppi-controller  1.3.12  np2py312h2ed9cc7_21  robostack-jazzy

# Build dependencies from the affected artifact's rendered_recipe.yaml
GCC 14.4.0 / xtensor 0.24.7 / xsimd 10.0.0 / xtl 0.7.7

Environment info

Ubuntu 24.04 / ROS 2 Jazzy / linux-64

Start with nav2_mppi_controller/src/optimizer.cpp and nav2_mppi_controller/CMakeLists.txt at Nav2 1.3.12, then inspect the affected artifact's info/recipe/rendered_recipe.yaml for xsimd and xtensor versions. Reproduce the standalone xsimd sine/cosine results and the straight-trajectory integration case. Done means the rebuilt MPPI package produces correct signs and forward commands under the reported Ubuntu 24.04 / ROS 2 Jazzy setup.