Implementation:Google deepmind Mujoco User Util

Knowledge Sources	Google_deepmind_Mujoco
Domains	Physics Simulation, Math Utilities
Last Updated	2026-02-15 04:00 GMT

Overview

Provides low-level mathematical and utility functions for vector operations, quaternion math, string parsing, and numeric validation used throughout the user module.

Description

user_util.cc contains foundational utility functions used across the MuJoCo user module. It implements vector operations (mjuu_setvec, mjuu_dot3, mjuu_dist3, mjuu_normvec, mjuu_scalevec), matrix address computation (mjuu_matadr), numeric validation (mjuu_defined using isnan), and provides overloaded versions for both double and float types. The file includes a macOS-specific workaround for locale-sensitive strtof/strtod functions to ensure consistent numeric parsing across platforms.

Usage

Used as a utility library by most files in the user and xml modules for basic mathematical operations and numeric conversions during model specification and compilation.

Code Reference

Source Location

• Repository: Google_deepmind_Mujoco
• File: src/user/user_util.cc
• Lines: 1-1282

Key Functions

bool mjuu_defined(double num);
int mjuu_matadr(int g1, int g2, int n);
void mjuu_setvec(double* dest, double x, double y, double z, double w);
void mjuu_setvec(float* dest, double x, double y, double z, double w);
void mjuu_setvec(double* dest, double x, double y, double z);
double mjuu_dot3(const double* a, const double* b);
double mjuu_dist3(const double* a, const double* b);
double mjuu_normvec(double* vec, int n);
void mjuu_scalevec(double* res, const double* vec, double s, int n);

Import

#include "user/user_util.h"

I/O Contract

Inputs

Name	Type	Required	Description
dest	double*/float*	Yes	Destination vector for set/copy operations
vec	double*/float*	Yes	Input vector for normalization/scaling
n	int	Yes	Vector dimension or matrix size
num	double	Yes (for mjuu_defined)	Numeric value to check for NaN

Outputs

Name	Type	Description
bool	bool	Whether a numeric value is defined (not NaN)
double	double	Computed dot product, distance, or previous vector length
void	void	Vectors modified in-place

Related Pages

• Environment:Google_deepmind_Mujoco_C_Build_Environment