The ARGoS Forum

Posted: **Tue Dec 10, 2013 4:01 pm**

Hi,

I am running argos3 simulation where sometimes I need to remove an entity from a family of entity types. Rarely I get this error:

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[FATAL] CSpace::RemoveEntity() : Entity "pellet509" has not been found in the indexes.

which quits the application. I am not sure what I am doing wrong. Here is my code for how the entities are created:

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std::ostringstream pelletId;
pelletId << "pellet" << pelletIdCounter;
CBoxEntity* pellet = new CBoxEntity(pelletId.str(),CVector3(robotPosition + CVector3(0.1,0.1,0)),CQuaternion(),true,CVector3(0.1,0.1,0.1),0.1);
AddEntity(*pellet);
pellets.push_back(pellet);
pelletIdCounter++;

where pellets is a vector of pointers to the CBoxEntities.

Then at some point later in the simulation, I randomly remove a pellet:

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if (pellets.size() > 0) {
    uint pelletId = uint(randNumGenerator->Uniform(CRange<Real>(0,pellets.size()-1)));
    //-- try if it still exists in space indexes
   CSpace::TMapPerType& pelletsInSpace = GetSpace().GetEntitiesByType("box");
   CBoxEntity* pellet = any_cast<CBoxEntity*>(pelletsInSpace[pellets[pelletId]->GetId()]);
   if (pellet != NULL) {
      RemoveEntity(*pellet);
   }
   //-- remove from the array
   pellets.erase(pellets.begin()+pelletId);
   pellet = NULL;
}

As you can see, I thought if I specifically double-check if the pellet can actually be found by trying to find it by its id between all box entities, it should be fine. Yet I still get the error. Is there a better way of doing this?

Posted: **Tue Dec 10, 2013 5:39 pm**

Hi,

I tried the following code:

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   randNumGenerator = CRandom::CreateRNG("argos");
   CBoxEntity* b;
   for(size_t i = 0; i < 5000; ++i) {
      b = new CBoxEntity("b" + ToString(i),
                         CVector3(0.1f + i * 0.2f, 0.1f, 0.0f),
                         CQuaternion(),
                         true,
                         CVector3(0.1f, 0.1f, 0.1f),
                         0.1f);
      AddEntity(*b);
      pellets.push_back(b);
      fprintf(stderr, "[DEBUG] Added box '%s'\n", b->GetId().c_str());
   }

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   fprintf(stderr, "[DEBUG] \n[DEBUG] %d entities left\n", pellets.size());
   if(! pellets.empty()) {
      UInt32 pelletId = randNumGenerator->Uniform(CRange<UInt32>(0,pellets.size()));
      CSpace::TMapPerType& pelletsInSpace = GetSpace().GetEntitiesByType("box");
      CBoxEntity* pellet = any_cast<CBoxEntity*>(pelletsInSpace[pellets[pelletId]->GetId()]);
      if (pellet != NULL) {
         fprintf(stderr, "[DEBUG] Removing box '%s'...", pellet->GetId().c_str());
         RemoveEntity(*pellet);
         fprintf(stderr, "done.\n");
      }
      pellets.erase(pellets.begin()+pelletId);
   }

That is functionally equivalent to yours. The only (irrelevant) modification is:

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UInt32 pelletId = randNumGenerator->Uniform(CRange<UInt32>(0,pellets.size()));

that fixes a couple of bugs in the code you posted.

I tried this with multiple random seeds and 5000 boxes, and never managed to reproduce your problem

Cheers,
Carlo

The ARGoS Forum

Removing entities sometimes doesn't work

Removing entities sometimes doesn't work

Re: Removing entities sometimes doesn't work