Make constraint island discovery on by default.

Also fix latent bug in mjData serialization.

PiperOrigin-RevId: 799505349
Change-Id: I299e7cc8133fa2ec0b339a7ff3d02543e06778b1

src/engine/engine_forward.c

@@ -723,7 +723,7 @@ void mj_fwdConstraint(const mjModel* m, mjData* d) {
   mju_zeroInt(d->solver_niter, mjNISLAND);
 
   // check if islands are supported
-  int islands_supported = mjENABLED(mjENBL_ISLAND)      &&
+  int islands_supported = !mjDISABLED(mjDSBL_ISLAND)    &&
                           nisland > 0                   &&
                           m->opt.noslip_iterations == 0 &&
                           (m->opt.solver == mjSOL_CG || m->opt.solver == mjSOL_NEWTON);

src/engine/engine_island.c

@@ -411,7 +411,7 @@ void mj_island(const mjModel* m, mjData* d) {
   int nv = m->nv, nefc = d->nefc, ntree=m->ntree;
 
   // no constraints: quick return
-  if (!mjENABLED(mjENBL_ISLAND) || !nefc) {
+  if (mjDISABLED(mjDSBL_ISLAND) || !nefc) {
     d->nisland = d->nidof = 0;
     return;
   }
@@ -454,7 +454,7 @@ void mj_island(const mjModel* m, mjData* d) {
     return;
   }
 
-  // count ni: total number of dofs in islands
+  // count nidof: total number of dofs in islands
   int nidof = 0;
   for (int i=0; i < nv; i++) {
     nidof += (tree_island[m->dof_treeid[i]] >= 0);

src/engine/engine_support.c

@@ -62,7 +62,8 @@ const char* mjDISABLESTRING[mjNDISABLE] = {
   "Midphase",
   "Eulerdamp",
   "AutoReset",
-  "NativeCCD"
+  "NativeCCD",
+  "Island"
 };
 
 
@@ -72,8 +73,7 @@ const char* mjENABLESTRING[mjNENABLE] = {
   "Energy",
   "Fwdinv",
   "InvDiscrete",
-  "MultiCCD",
-  "Island"
+  "MultiCCD"
 };
 
 

src/experimental/usd/plugins/mjcf/mujoco_to_usd.cc

@@ -643,7 +643,6 @@ class ModelWriter {
 
     const std::vector<std::pair<pxr::TfToken, int>> enable_flags = {
         {MjcPhysicsTokens->mjcFlagMulticcd, mjENBL_MULTICCD},
-        {MjcPhysicsTokens->mjcFlagIsland, mjENBL_ISLAND},
         {MjcPhysicsTokens->mjcFlagFwdinv, mjENBL_FWDINV},
         {MjcPhysicsTokens->mjcFlagEnergy, mjENBL_ENERGY},
         {MjcPhysicsTokens->mjcFlagOverride, mjENBL_OVERRIDE},
@@ -669,7 +668,8 @@ class ModelWriter {
         {MjcPhysicsTokens->mjcFlagMidphase, mjDSBL_MIDPHASE},
         {MjcPhysicsTokens->mjcFlagEulerdamp, mjDSBL_EULERDAMP},
         {MjcPhysicsTokens->mjcFlagAutoreset, mjDSBL_AUTORESET},
-        {MjcPhysicsTokens->mjcFlagNativeccd, mjDSBL_NATIVECCD}};
+        {MjcPhysicsTokens->mjcFlagNativeccd, mjDSBL_NATIVECCD},
+        {MjcPhysicsTokens->mjcFlagIsland, mjDSBL_ISLAND}};
     for (const auto &[token, flag] : disable_flags) {
       create_flag_attr(token, flag, false);
     }

src/experimental/usd/usd_to_mjspec.cc

@@ -617,6 +617,10 @@ void ParseUsdPhysicsScene(mjSpec* spec,
   mjc_physics_scene.GetAutoResetFlagAttr().Get(&autoreset_flag);
   spec->option.disableflags |= (!autoreset_flag ? mjDSBL_AUTORESET : 0);
 
+  bool island_flag;
+  mjc_physics_scene.GetIslandFlagAttr().Get(&island_flag);
+  spec->option.disableflags |= (!island_flag ? mjDSBL_ISLAND : 0);
+
   bool override_flag;
   mjc_physics_scene.GetOverrideFlagAttr().Get(&override_flag);
   spec->option.enableflags |= (override_flag ? mjENBL_OVERRIDE : 0);
@@ -637,10 +641,6 @@ void ParseUsdPhysicsScene(mjSpec* spec,
   mjc_physics_scene.GetMultiCCDFlagAttr().Get(&multiccd_flag);
   spec->option.enableflags |= (multiccd_flag ? mjENBL_MULTICCD : 0);
 
-  bool island_flag;
-  mjc_physics_scene.GetIslandFlagAttr().Get(&island_flag);
-  spec->option.enableflags |= (island_flag ? mjENBL_ISLAND : 0);
-
   // Compiler attributes
   auto auto_limits_attr = mjc_physics_scene.GetAutoLimitsAttr();
   if (auto_limits_attr.HasAuthoredValue()) {

src/xml/xml_native_reader.cc

@@ -121,7 +121,7 @@ const char* MJCF[nMJCF][mjXATTRNUM] = {
         {"flag", "?", "23", "constraint", "equality", "frictionloss", "limit", "contact",
             "passive", "gravity", "clampctrl", "warmstart",
             "filterparent", "actuation", "refsafe", "sensor", "midphase", "eulerdamp", "autoreset",
-            "override", "energy", "fwdinv", "invdiscrete", "multiccd", "island", "nativeccd"},
+            "nativeccd", "island", "override", "energy", "fwdinv", "invdiscrete", "multiccd"},
     {">"},
 
     {"size", "*", "14", "memory", "njmax", "nconmax", "nstack", "nuserdata", "nkey",
@@ -1199,6 +1199,7 @@ void mjXReader::Option(XMLElement* section, mjOption* opt) {
     READDSBL("eulerdamp",    mjDSBL_EULERDAMP)
     READDSBL("autoreset",    mjDSBL_AUTORESET)
     READDSBL("nativeccd",    mjDSBL_NATIVECCD)
+    READDSBL("island",       mjDSBL_ISLAND)
 #undef READDSBL
 
 #define READENBL(NAME, MASK) \
@@ -1211,7 +1212,6 @@ void mjXReader::Option(XMLElement* section, mjOption* opt) {
     READENBL("fwdinv",      mjENBL_FWDINV)
     READENBL("invdiscrete", mjENBL_INVDISCRETE)
     READENBL("multiccd",    mjENBL_MULTICCD)
-    READENBL("island",      mjENBL_ISLAND)
 #undef READENBL
   }
 }

src/xml/xml_native_writer.cc

@@ -1056,6 +1056,7 @@ void mjXWriter::Option(XMLElement* root) {
     WRITEDSBL("eulerdamp",      mjDSBL_EULERDAMP)
     WRITEDSBL("autoreset",      mjDSBL_AUTORESET)
     WRITEDSBL("nativeccd",      mjDSBL_NATIVECCD)
+    WRITEDSBL("island",         mjDSBL_ISLAND)
 #undef WRITEDSBL
 
 #define WRITEENBL(NAME, MASK) \
@@ -1066,7 +1067,6 @@ void mjXWriter::Option(XMLElement* root) {
     WRITEENBL("fwdinv",         mjENBL_FWDINV)
     WRITEENBL("invdiscrete",    mjENBL_INVDISCRETE)
     WRITEENBL("multiccd",       mjENBL_MULTICCD)
-    WRITEENBL("island",         mjENBL_ISLAND)
 #undef WRITEENBL
   }