add computation graph (#75)

src/computation_graph.cc

@@ -0,0 +1,25 @@
+#include "computation_graph.h"
+
+OperationId ComputationGraph::add_operation(std::unique_ptr<Operation> operation) {
+  OperationId operationid = operations_.size();
+  OperationId creator_operationid = operation->creator_operationid();
+  if (spawned_operations_.size() != operationid) {
+    ORCH_LOG(ORCH_FATAL, "ComputationGraph is attempting to call add_operation, but spawned_operations_.size() != operationid.");
+  }
+  operations_.emplace_back(std::move(operation));
+  if (creator_operationid != NO_OPERATION && creator_operationid != ROOT_OPERATION) {
+    spawned_operations_[creator_operationid].push_back(operationid);
+  }
+  spawned_operations_.push_back(std::vector<OperationId>());
+  return operationid;
+}
+
+const Task& ComputationGraph::get_task(OperationId operationid) {
+  if (operationid >= operations_.size()) {
+    ORCH_LOG(ORCH_FATAL, "ComputationGraph attempting to get_task with operationid " << operationid << ", but operationid >= operations_.size().");
+  }
+  if (!operations_[operationid]->has_task()) {
+    ORCH_LOG(ORCH_FATAL, "Calling get_task with operationid " << operationid << ", but this corresponds to a push not a task.");
+  }
+  return operations_[operationid]->task();
+}