chenlin/Mujoco_WASM
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Convert qLD to CSR format.

Browse Source 
PiperOrigin-RevId: 728196818
Change-Id: I31bdf32e251293284426ed345019f27fd051a0e1
This commit is contained in:
Yuval Tassa
2025-02-18 07:13:49 -08:00
committed by Copybara-Service
parent 9fb4ec95f8
commit fb07e0d1f7
23 changed files with 160 additions and 159 deletions
Download Patch File Download Diff File Expand all files Collapse all files
doc/programming/simulation.rst
+7 -5
View File
@@ -614,12 +614,14 @@ essential to keep it in mind at all times. All MuJoCo utility functions that ope
:ref:`mju_mulMatMat`, :ref:`mju_mulMatVec` etc. assume this matrix layout. For vectors there is of course no
difference between row-major and column-major formats.
.. TODO(tassa): update this section when qM is migrated to CSR.
When possible, MuJoCo exploits sparsity. This can make all the difference between O(N) and O(N^3) scaling. The inertia
matrix ``mjData.qM`` and its LTDL factorization ``mjData.qLD`` are always represented as sparse, using a custom
indexing format designed for matrices that correspond to tree topology. The functions :ref:`mj_factorM`,
:ref:`mj_solveM`, :ref:`mj_solveM2` and :ref:`mj_mulM` are used for sparse factorization, substitution and
matrix-vector multiplication. The user can also convert these matrices to dense format with the function
:ref:`mj_fullM` although MuJoCo never does that internally.
matrix ``mjData.qM`` and its LTDL factorization ``mjData.qLD`` are always represented as sparse. ``qM`` uses a custom
indexing format designed for matrices that correspond to tree topology, while ``qLD`` uses the standard CSR format.
``qM`` will be migrated to CSR in and upcoming change. The functions :ref:`mj_factorM`, :ref:`mj_solveM`,
:ref:`mj_solveM2` and :ref:`mj_mulM` are used for sparse factorization, substitution and matrix-vector multiplication.
The user can also convert these matrices to dense format with the function :ref:`mj_fullM` although MuJoCo never does
that internally.
The constraint Jacobian matrix ``mjData.efc_J`` is represented as sparse whenever the sparse Jacobian option is
enabled. The function :ref:`mj_isSparse` can be used to determine if sparse format is currently in use. In that case