Switch mjData.{qH,qLD} from reduced ("C") to full ("M") inertia matrix structure. No performance impact of extra zeros because of existing "simple dof" skipping mechanism.

PiperOrigin-RevId: 733523931
Change-Id: Ic8d8a152dda5532331c239cb6b4ce7d8d09b7fff

mjx/mujoco/mjx/_src/io.py

@@ -372,7 +372,7 @@ def make_data(
         'efc_aref': (nefc, float),
         'efc_force': (nefc, float),
         '_qM_sparse': (m.nM, float),
-        '_qLD_sparse': (m.nC, float),
+        '_qLD_sparse': (m.nM, float),
         '_qLDiagInv_sparse': (m.nv, float),
     }
 
@@ -511,7 +511,7 @@ def get_data_into(
         value = value[dof_i, dof_j]
       elif field.name == 'qLD' and not support.is_sparse(m):
         # TODO(erikfrey): provide correct qLDs
-        value = np.zeros(m.nC)
+        value = np.zeros(m.nM)
       elif field.name == 'qLDiagInv' and not support.is_sparse(m):
         value = np.ones(m.nv)
 

mjx/mujoco/mjx/_src/smooth_test.py

@@ -92,8 +92,8 @@ class SmoothTest(absltest.TestCase):
     # factor_m
     dx = jax.jit(mjx.factor_m)(mx, mjx.put_data(m, d))
     qLDLegacy = np.zeros(mx.nM)  # pylint:disable=invalid-name
-    for i in range(m.nC):
-      qLDLegacy[d.mapM2C[i]] = d.qLD[i]
+    for i in range(m.nM):
+      qLDLegacy[d.mapM2M[i]] = d.qLD[i]
     _assert_eq(qLDLegacy, dx.qLD, 'qLD')
     _assert_attr_eq(d, dx, 'qLDiagInv')
     _assert_eq(dx._qLD_sparse, np.zeros(0), '_qLD_sparse')

mjx/mujoco/mjx/_src/types.py

@@ -1352,7 +1352,7 @@ class Data(PyTreeNode):
     efc_aref: reference pseudo-acceleration                     (nefc,)
     efc_force: constraint force in constraint space             (nefc,)
     _qM_sparse: qM in sparse representation                     (nM,)
-    _qLD_sparse: qLD in sparse representation                   (nC,)
+    _qLD_sparse: qLD in sparse representation                   (nM,)
     _qLDiagInv_sparse: qLDiagInv in sparse representation       (nv,)
   """  # fmt: skip
   # constant sizes: