Repast HPC has a compiler macro definition in AgentImporterExporter.h called "SHARE_AGENTS_BY_SET". Provided that this macro is defined, Repast HPC has the ability to request and synchronize specific sets of agents. (This function adds a small overhead and can decrease performance; if this is problematic, it is possible to remove this functionality simply by removing the macro definition and recompiling Repast HPC.) The ability to work with named groups of requested agents carries two implications:
In this demo we will focus only on the first implication: the ability to request agents in sets, and synchronize only specific sets.
The theory behind this feature is simple: suppose you have a large category of agents of one kind, and a small category of agents of another kind- say, teachers and students, with many students but relatively few teachers. Imagine that your simulation reaches a point where it needs to update non-local copies, but only of the teachers, but not of the students. Updating all of the agents, including both students and teachers, would be an expensive operation, but the cost is lower if only the teachers need to be updates. Repast HPC allows this.
For this demo, we eliminate some of the unneeded methods in RepastHPCDemoModel class, and make the following modification to the 'requestAgents' method:
void RepastHPCDemoModel::requestAgents(){
int rank = repast::RepastProcess::instance()->rank();
int worldSize= repast::RepastProcess::instance()->worldSize();
repast::AgentRequest req1(rank);
if(rank == 1){
repast::AgentId id1(1,0,0,0);
repast::AgentId id2(2,0,0,0);
req1.addRequest(id1);
req1.addRequest(id2);
}
repast::RepastProcess::instance()->requestAgents<RepastHPCDemoAgent, RepastHPCDemoAgentPackage, RepastHPCDemoAgentPackageProvider, RepastHPCDemoAgentPackageReceiver>(context, req1, *provider, *receiver, *receiver, "SET_1");
repast::AgentRequest req2(rank);
if(rank == 1){
repast::AgentId id1(3,0,0,0);
repast::AgentId id2(4,0,0,0);
req2.addRequest(id1);
req2.addRequest(id2);
}
repast::RepastProcess::instance()->requestAgents<RepastHPCDemoAgent, RepastHPCDemoAgentPackage, RepastHPCDemoAgentPackageProvider, RepastHPCDemoAgentPackageReceiver>(context, req2, *provider, *receiver, *receiver, "SET_2");
}
Notice that this makes two requests (both of them from Process 1 to Process 0), and adds a name to each of the requests, "SET_1" and "SET_2". Using this, we make the following modification to the 'doSomething' method:
void RepastHPCDemoModel::doSomething(){
int whichRank = 1;
if(repast::RepastProcess::instance()->rank() == whichRank) std::cout << " TICK " << repast::RepastProcess::instance()->getScheduleRunner().currentTick() << std::endl;
if(repast::RepastProcess::instance()->rank() == whichRank){
std::cout << "LOCAL AGENTS:" << std::endl;
for(int r = 0; r < 4; r++){
for(int i = 0; i < 10; i++){
repast::AgentId toDisplay(i, r, 0);
RepastHPCDemoAgent* agent = context.getAgent(toDisplay);
if((agent != 0) && (agent->getId().currentRank() == whichRank)) std::cout << agent->getId() << " " << agent->getC() << " " << agent->getTotal() << std::endl;
}
}
std::cout << "NON LOCAL AGENTS:" << std::endl;
for(int r = 0; r < 4; r++){
for(int i = 0; i < 10; i++){
repast::AgentId toDisplay(i, r, 0);
RepastHPCDemoAgent* agent = context.getAgent(toDisplay);
if((agent != 0) && (agent->getId().currentRank() != whichRank)) std::cout << agent->getId() << " " << agent->getC() << " " << agent->getTotal() << std::endl;
}
}
}
std::vector<RepastHPCDemoAgent*> agents;
context.selectAgents(repast::SharedContext<RepastHPCDemoAgent>::LOCAL, countOfAgents, agents);
std::vector<RepastHPCDemoAgent*>::iterator it = agents.begin();
while(it != agents.end()){
(*it)->play(&context);
it++;
}
repast::RepastProcess::instance()->synchronizeAgentStates<RepastHPCDemoAgentPackage, RepastHPCDemoAgentPackageProvider, RepastHPCDemoAgentPackageReceiver>(*provider, *receiver, "SET_1");
}
The first just changes the rank that will give us output- we want to look at Rank 1, not Rank 0. But the key change is the addition of a set name in the synchronizeAgentStates method. By adding this, the only agents that will be updated will be those in SET_1, and not those in SET_2. We can see this when we examine the output:
TICK 2
LOCAL AGENTS:
AgentId(0, 1, 0, 1) 100 200
AgentId(1, 1, 0, 1) 100 200
AgentId(2, 1, 0, 1) 100 200
AgentId(3, 1, 0, 1) 100 200
AgentId(4, 1, 0, 1) 100 200
NON LOCAL AGENTS:
AgentId(1, 0, 0, 0) 100 200
AgentId(2, 0, 0, 0) 100 200
AgentId(3, 0, 0, 0) 100 200
AgentId(4, 0, 0, 0) 100 200
TICK 3
LOCAL AGENTS:
AgentId(0, 1, 0, 1) 108 218
AgentId(1, 1, 0, 1) 100 209
AgentId(2, 1, 0, 1) 107 227
AgentId(3, 1, 0, 1) 101 221
AgentId(4, 1, 0, 1) 107 220
NON LOCAL AGENTS:
AgentId(1, 0, 0, 0) 108 211
AgentId(2, 0, 0, 0) 108 218
AgentId(3, 0, 0, 0) 100 200
AgentId(4, 0, 0, 0) 100 200
TICK 4
LOCAL AGENTS:
AgentId(0, 1, 0, 1) 108 234
AgentId(1, 1, 0, 1) 101 230
AgentId(2, 1, 0, 1) 115 238
AgentId(3, 1, 0, 1) 115 245
AgentId(4, 1, 0, 1) 108 241
NON LOCAL AGENTS:
AgentId(1, 0, 0, 0) 115 224
AgentId(2, 0, 0, 0) 122 242
AgentId(3, 0, 0, 0) 100 200
AgentId(4, 0, 0, 0) 100 200
TICK 5
LOCAL AGENTS:
AgentId(0, 1, 0, 1) 122 251
AgentId(1, 1, 0, 1) 116 245
AgentId(2, 1, 0, 1) 117 243
AgentId(3, 1, 0, 1) 122 265
AgentId(4, 1, 0, 1) 108 264
NON LOCAL AGENTS:
AgentId(1, 0, 0, 0) 123 235
AgentId(2, 0, 0, 0) 129 262
AgentId(3, 0, 0, 0) 100 200
AgentId(4, 0, 0, 0) 100 200
The key is to notice that the non-local copies of Agents(3,0,0,0) and (4,0,0,0) that exist on Process 1 are not being updated, even though Agents(1,0,0,0) and (2,0,0,0) are. The originals of all four agents on Process 0 are being update, but not the non-local copies of the agents in SET_2.