[Scheduler] Fix scheduling of producer node in graph outputs

Handle case where producer nodes are also graph outputs,
in this case the initial list of consumers may contain producer
nodes.

They are now scheduled as requiredProducers instead
of runnableConsumers.

It actually does not change the effective scheduling, though it
handles more uniformely producers nodes (outputs of the graph or not).

Added some test cases in Test_scheduler.cpp.

src/scheduler/Scheduler.cpp

@@ -77,6 +77,9 @@ std::vector<Aidge::Scheduler::StaticSchedulingElement*> Aidge::Scheduler::genera
     // we should always consume available data first. This is ensured
     // by setting the consumers list to the output nodes and then recursively
     // find the dependencies.
+    // The initial list may contain producer nodes, in which case
+    // getPriorProducersConsumers() at step 2 will have moved it in
+    // the requiredProducers list.
     std::set<std::shared_ptr<Node>> consumers = mGraphView->outputNodes();
     std::set<std::shared_ptr<Node>> producers;
 
@@ -737,7 +740,9 @@ Aidge::Scheduler::getPriorProducersConsumers(const std::shared_ptr<Node>& node)
     }
 
     prior.isPrior = true;
-    if (prior.priorConsumers.empty()) {
+    if (node->type() == Producer_Op::Type) {
+        prior.requiredProducers.insert(node);
+    } else if (prior.priorConsumers.empty()) {
         prior.priorConsumers.insert(node);
     }
     mPriorCache.insert(std::make_pair(node, prior));

unit_tests/scheduler/Test_Scheduler.cpp

@@ -26,6 +26,8 @@
 #include "aidge/graph/Testing.hpp"
 #include "aidge/operator/GenericOperator.hpp"
 #include "aidge/operator/Producer.hpp"
+#include "aidge/operator/Identity.hpp"
+#include "aidge/operator/GenericOperator.hpp"
 #include "aidge/scheduler/SequentialScheduler.hpp"
 
 namespace Aidge {
@@ -134,4 +136,58 @@ TEST_CASE("randomScheduling", "[Scheduler][randomGen]") {
   fmt::print("nbUnicity = {}/{}\n", nbUnicity, nbTests);
 }
 
+TEST_CASE("someScheduling", "[Scheduler][someUseCases]") {
+
+  SECTION("Identity Graph") {
+    auto data1 = Producer({1}, "data1");
+    auto identity = Identity("id");
+    auto g = std::make_shared<GraphView>("TestGraph");
+    data1->addChild(identity);
+    g->add({data1, identity});
+    auto scheduler = SequentialScheduler(g);
+    scheduler.generateScheduling();
+    const auto sch = scheduler.getStaticScheduling();
+    const auto nodes = g->getNodes();
+    REQUIRE(sch.size() == nodes.size());
+    REQUIRE(sch[0] == data1);
+    REQUIRE(sch[1] == identity);
+  }
+
+  SECTION("Producer Graph") {
+    auto data1 = Producer({1}, "data1");
+    auto g = std::make_shared<GraphView>("TestGraph");
+    g->add({data1});
+    auto scheduler = SequentialScheduler(g);
+    scheduler.generateScheduling();
+    const auto sch = scheduler.getStaticScheduling();
+    const auto nodes = g->getNodes();
+    REQUIRE(sch.size() == nodes.size());
+    REQUIRE(sch[0] == data1);
+  }
+
+  SECTION("Generic producer Graph") {
+    auto gen1 = GenericOperator("Prod", 0, 0, 1, "gen1");
+    auto g = std::make_shared<GraphView>("TestGraph");
+    g->add({gen1});
+    auto scheduler = SequentialScheduler(g);
+    scheduler.generateScheduling();
+    const auto sch = scheduler.getStaticScheduling();
+    const auto nodes = g->getNodes();
+    REQUIRE(sch.size() == nodes.size());
+    REQUIRE(sch[0] == gen1);
+  }
+
+  SECTION("No output Graph") {
+    auto dead1 = GenericOperator("Dead", 1, 0, 0, "dead");
+    auto g = std::make_shared<GraphView>("TestGraph");
+    g->add({dead1});
+    auto scheduler = SequentialScheduler(g);
+    scheduler.generateScheduling();
+    const auto sch = scheduler.getStaticScheduling();
+    const auto nodes = g->getNodes();
+    REQUIRE(nodes.size() == 1);
+    REQUIRE(sch.size() == 0);
+  }
+}
+
 } // namespace Aidge