rollout exchange chunk_divisor arg for chunk_size

python/mujoco/rollout.cc

@@ -50,8 +50,8 @@ Roll out open-loop trajectories from initial states, get resulting states and se
   output arguments (optional):
     state              (nroll x nstep x nstate)       nroll nstep states
     sensordata         (nroll x nstep x nsendordata)  nroll trajectories of nstep sensordata vectors
-    chunk_divisor      integer, determines threadpool chunk size according to
-                                chunk_size = max(1, nroll / (nthread * chunk_divisor)
+    chunk_size         integer, determines threadpool chunk size. If unspecified
+                                chunk_size = max(1, nroll / (nthread * 10)
 )";
 
 // C-style rollout function, assumes all arguments are valid
@@ -241,7 +241,7 @@ PYBIND11_MODULE(_rollout, pymodule) {
          std::optional<const PyCArray> control,
          std::optional<const PyCArray> state,
          std::optional<const PyCArray> sensordata,
-         int chunk_divisor
+         std::optional<int> chunk_size
          ) {
         // get raw pointers
         int nroll = state0.shape(0);
@@ -281,11 +281,17 @@ PYBIND11_MODULE(_rollout, pymodule) {
 
           // call unsafe rollout function
           if (nthread > 1 && nroll > 1) {
-            int chunk_size = std::max(1, nroll / (chunk_divisor * nthread));
+            int chunk_size_final = 1;
+            if (!chunk_size.has_value()) {
+              chunk_size_final = std::max(1, nroll / (10 * nthread));
+            }
+            else {
+              chunk_size_final = *chunk_size;
+            }
             InterceptMjErrors(_unsafe_rollout_threaded)(
                 model_ptrs, data_ptrs, nroll, nstep, control_spec, state0_ptr,
                 warmstart0_ptr, control_ptr, state_ptr, sensordata_ptr,
-                nthread, chunk_size);
+                nthread, chunk_size_final);
           }
           else {
             InterceptMjErrors(_unsafe_rollout)(
@@ -303,7 +309,7 @@ PYBIND11_MODULE(_rollout, pymodule) {
       py::arg("control")    = py::none(),
       py::arg("state")      = py::none(),
       py::arg("sensordata") = py::none(),
-      py::arg("chunk_divisor") = 10,
+      py::arg("chunk_size") = py::none(),
       py::doc(rollout_doc)
   );
 }

python/mujoco/rollout.py

@@ -35,7 +35,7 @@ def rollout(
     initial_warmstart: Optional[npt.ArrayLike] = None,
     state: Optional[npt.ArrayLike] = None,
     sensordata: Optional[npt.ArrayLike] = None,
-    chunk_divisor: int = 10,
+    chunk_size: int = None,
 ):
   """Rolls out open-loop trajectories from initial states, get subsequent states and sensor values.
 
@@ -60,8 +60,8 @@ def rollout(
       (nroll x nstep x nstate)
     sensordata: Sensor data output array (optional).
       (nroll x nstep x nsensordata)
-    chunk_divisor: Determines threadpool chunk size according to
-                   chunk_size = max(1, nroll / (nthread * chunk_divisor)
+    chunk_size: Determines threadpool chunk size. If unspecified,
+                chunk_size = max(1, nroll / (nthread * 10)
 
   Returns:
     state:
@@ -88,7 +88,7 @@ def rollout(
         control,
         state,
         sensordata,
-        chunk_divisor,
+        chunk_size,
     )
     return state, sensordata
 
@@ -102,6 +102,8 @@ def rollout(
   # check types
   if nstep and not isinstance(nstep, int):
     raise ValueError('nstep must be an integer')
+  if chunk_size and not isinstance(chunk_size, int):
+    raise ValueError('chunk_size must be an integer')
   _check_must_be_numeric(
       initial_state=initial_state,
       initial_warmstart=initial_warmstart,
@@ -202,7 +204,7 @@ def rollout(
       control,
       state,
       sensordata,
-      chunk_divisor,
+      chunk_size,
   )
 
   # return outputs