Adding support of transient federates

core/src/main/java/org/lflang/AttributeUtils.java

@@ -226,6 +226,11 @@ public static boolean isSparse(EObject node) {
     return findAttributeByName(node, "sparse") != null;
   }
 
+  /** Return true if the node has an {@code @transient} attribute. */
+  public static boolean isTransient(Instantiation node) {
+    return findAttributeByName(node, "transient") != null;
+  }
+
   /** Return true if the reactor is marked to be a federate. */
   public static boolean isFederate(Reactor reactor) {
     return findAttributeByName(reactor, "_fed_config") != null;

core/src/main/java/org/lflang/federated/extensions/CExtension.java

@@ -464,7 +464,7 @@ public String generatePortAbsentReactionBody(
                 + receivingPortID
                 + ", "
                 + connection.getDstFederate().id
-                + ", (long long) lf_time_logical_elapsed());",
+                + ", lf_time_logical_elapsed());",
             "if (" + sendRef + " == NULL || !" + sendRef + "->is_present) {",
             "LF_PRINT_LOG(\"The output port is NULL or it is not present.\");",
             "    lf_send_port_absent_to_federate("
@@ -553,15 +553,33 @@ protected String makePreamble(
     // that handles incoming network messages destined to the specified
     // port. This will only be used if there are federates.
     int numOfNetworkActions = federate.networkMessageActions.size();
+    int numZDCNetworkActions = federate.zeroDelayCycleNetworkMessageActions.size();
     code.pr(
         """
         interval_t _lf_action_delay_table[%1$s];
         lf_action_base_t* _lf_action_table[%1$s];
         size_t _lf_action_table_size = %1$s;
-        lf_action_base_t* _lf_zero_delay_cycle_action_table[%2$s];
-        size_t _lf_zero_delay_cycle_action_table_size = %2$s;
         """
-            .formatted(numOfNetworkActions, federate.zeroDelayCycleNetworkMessageActions.size()));
+            .formatted(numOfNetworkActions));
+    if (numZDCNetworkActions > 0) {
+      code.pr(
+          """
+          lf_action_base_t* _lf_zero_delay_cycle_action_table[%1$s];
+          size_t _lf_zero_delay_cycle_action_table_size = %1$s;
+          uint16_t _lf_zero_delay_cycle_upstream_ids[%1$s];
+          bool _lf_zero_delay_cycle_upstream_disconnected[%1$s] = { false };
+          """
+              .formatted(numZDCNetworkActions));
+    } else {
+      // Make sure these symbols are defined, even though only size will be used.
+      code.pr(
+          """
+          lf_action_base_t** _lf_zero_delay_cycle_action_table = NULL;
+          size_t _lf_zero_delay_cycle_action_table_size = 0;
+          uint16_t* _lf_zero_delay_cycle_upstream_ids = NULL;
+          bool* _lf_zero_delay_cycle_upstream_disconnected = NULL;
+          """);
+    }
 
     int numOfNetworkReactions = federate.networkReceiverReactions.size();
     code.pr(
@@ -723,6 +741,8 @@ else if (globalSTP instanceof CodeExprImpl)
     }
     // Set global variable identifying the federate.
     code.pr("_lf_my_fed_id = " + federate.id + ";");
+    // Set indicator variable that specifies whether the federate is transient or not.
+    code.pr("_fed.is_transient = " + federate.isTransient + ";");
 
     // We keep separate record for incoming and outgoing p2p connections to allow incoming traffic
     // to be processed in a separate

core/src/main/java/org/lflang/federated/extensions/CExtensionUtils.java

@@ -53,7 +53,6 @@ public static String initializeTriggersForNetworkActions(
     CodeBuilder code = new CodeBuilder();
     if (!federate.networkMessageActions.isEmpty()) {
       var actionTableCount = 0;
-      var zeroDelayActionTableCount = 0;
       for (int i = 0; i < federate.networkMessageActions.size(); ++i) {
         // Find the corresponding ActionInstance.
         Action action = federate.networkMessageActions.get(i);
@@ -76,10 +75,17 @@ public static String initializeTriggersForNetworkActions(
         // Set the ID of the source federate.
         code.pr(
             trigger + ".source_id = " + federate.networkMessageSourceFederate.get(i).id + "; \\");
-        if (federate.zeroDelayCycleNetworkMessageActions.contains(action)) {
+        int j = federate.zeroDelayCycleNetworkMessageActions.indexOf(action);
+        if (j >= 0) {
+          var upstream = federate.zeroDelayCycleNetworkUpstreamFeds.get(j);
+          code.pr("_lf_zero_delay_cycle_upstream_ids[" + j + "] = " + upstream.id + "; \\");
+          if (upstream.isTransient) {
+            // Transient federates are assumed to be initially disconnected.
+            code.pr("_lf_zero_delay_cycle_upstream_disconnected[" + j + "] = true; \\");
+          }
           code.pr(
               "_lf_zero_delay_cycle_action_table["
-                  + zeroDelayActionTableCount++
+                  + j
                   + "] = (lf_action_base_t*)&"
                   + trigger
                   + "; \\");
@@ -151,7 +157,8 @@ public static String stpStructs(FederateInstance federate) {
    */
   public static String createPortStatusFieldForInput(Input input) {
     StringBuilder builder = new StringBuilder();
-    // If it is not a multiport, then we could re-use the port trigger, and nothing needs to be done
+    // If it is not a multiport, then we could re-use the port trigger, and nothing
+    // needs to be done
     if (ASTUtils.isMultiport(input)) {
       // If it is a multiport, then create an auxiliary list of port
       // triggers for each channel of
@@ -236,12 +243,13 @@ static boolean clockSyncIsOn(FederateInstance federate, RtiConfig rtiConfig) {
    *
    * <p>Clock synchronization can be enabled using the clock-sync target property.
    *
-   * @see <a
-   *     href="https://github.com/icyphy/lingua-franca/wiki/Distributed-Execution#clock-synchronization">Documentation</a>
+   * @see <a href=
+   *     "https://github.com/icyphy/lingua-franca/wiki/Distributed-Execution#clock-synchronization">Documentation</a>
    */
   public static void initializeClockSynchronization(
       FederateInstance federate, RtiConfig rtiConfig, MessageReporter messageReporter) {
-    // Check if clock synchronization should be enabled for this federate in the first place
+    // Check if clock synchronization should be enabled for this federate in the
+    // first place
     if (clockSyncIsOn(federate, rtiConfig)) {
       messageReporter
           .nowhere()
@@ -267,8 +275,8 @@ public static void initializeClockSynchronization(
    *
    * <p>Clock synchronization can be enabled using the clock-sync target property.
    *
-   * @see <a
-   *     href="https://github.com/icyphy/lingua-franca/wiki/Distributed-Execution#clock-synchronization">Documentation</a>
+   * @see <a href=
+   *     "https://github.com/icyphy/lingua-franca/wiki/Distributed-Execution#clock-synchronization">Documentation</a>
    */
   public static void addClockSyncCompileDefinitions(FederateInstance federate) {
 
@@ -311,8 +319,15 @@ public static void generateCMakeInclude(
         "add_compile_definitions(LF_SOURCE_DIRECTORY=\"" + fileConfig.srcPath + "\")");
     cmakeIncludeCode.pr(
         "add_compile_definitions(LF_PACKAGE_DIRECTORY=\"" + fileConfig.srcPkgPath + "\")");
+    // After federates have been divided, their root package directory is different.
     cmakeIncludeCode.pr(
-        "add_compile_definitions(LF_SOURCE_GEN_DIRECTORY=\"" + fileConfig.getSrcGenPath() + "\")");
+        "add_compile_definitions(LF_FED_PACKAGE_DIRECTORY=\""
+            + fileConfig.srcPkgPath
+            + File.separator
+            + "fed-gen"
+            + File.separator
+            + fileConfig.name
+            + "\")");
     cmakeIncludeCode.pr("add_compile_definitions(LF_FILE_SEPARATOR=\"" + File.separator + "\")");
     try (var srcWriter = Files.newBufferedWriter(cmakeIncludePath)) {
       srcWriter.write(cmakeIncludeCode.getCode());

core/src/main/java/org/lflang/federated/generator/FedASTUtils.java

@@ -287,9 +287,10 @@ private static void addNetworkReceiverReactor(
     connection.dstFederate.networkMessageSourceFederate.add(connection.srcFederate);
     connection.dstFederate.networkMessageActionDelays.add(connection.getDefinition().getDelay());
     if (connection.srcFederate.isInZeroDelayCycle()
-        && connection.getDefinition().getDelay() == null)
+        && connection.getDefinition().getDelay() == null) {
       connection.dstFederate.zeroDelayCycleNetworkMessageActions.add(networkAction);
-
+      connection.dstFederate.zeroDelayCycleNetworkUpstreamFeds.add(connection.srcFederate);
+    }
     // Get the largest STAA for any reaction triggered by the destination port.
     TimeValue maxSTAA = findMaxSTAA(connection, coordination);
 

core/src/main/java/org/lflang/federated/generator/FederateInstance.java

@@ -36,6 +36,7 @@
 import java.util.Set;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
+import org.lflang.AttributeUtils;
 import org.lflang.MessageReporter;
 import org.lflang.TimeValue;
 import org.lflang.ast.ASTUtils;
@@ -96,6 +97,7 @@ public FederateInstance(
     this.bankWidth = bankWidth;
     this.messageReporter = messageReporter;
     this.targetConfig = targetConfig;
+    this.isTransient = AttributeUtils.isTransient(instantiation);
 
     // If the instantiation is in a bank, then we have to append
     // the bank index to the name.
@@ -157,6 +159,9 @@ public Instantiation getInstantiation() {
   /** The integer ID of this federate. */
   public int id;
 
+  /** Type of the federate: transient if true, and peristent if false . */
+  public boolean isTransient = false;
+
   /**
    * The name of this federate instance. This will be the instantiation name, possibly appended with
    * "__n", where n is the bank position of this instance if the instantiation is of a bank of
@@ -188,6 +193,12 @@ public Instantiation getInstantiation() {
    */
   public List<Action> zeroDelayCycleNetworkMessageActions = new ArrayList<>();
 
+  /**
+   * List of upstream federates corresponding to actions in the zeroDelayCycleNetworkMessageActions
+   * list.
+   */
+  public List<FederateInstance> zeroDelayCycleNetworkUpstreamFeds = new ArrayList<>();
+
   /**
    * A set of federates with which this federate has an inbound connection There will only be one
    * physical connection even if federate A has defined multiple physical connections to federate B.

core/src/main/java/org/lflang/federated/launcher/FedLauncherGenerator.java

@@ -323,9 +323,17 @@ private String getRtiCommand(List<FederateInstance> federates, boolean isRemote)
     if (targetConfig.getOrDefault(TracingProperty.INSTANCE).isEnabled()) {
       commands.add("                        -t \\");
     }
+    // Identify the number of transient federates.
+    int transientFederatesNumber = 0;
+    for (FederateInstance federate : federates) {
+      if (federate.isTransient) {
+        transientFederatesNumber++;
+      }
+    }
     commands.addAll(
         List.of(
             "                        -n " + federates.size() + " \\",
+            "                        -nt " + transientFederatesNumber + " \\",
             "                        -c "
                 + targetConfig.getOrDefault(ClockSyncModeProperty.INSTANCE).toString()
                 + " \\"));

core/src/main/java/org/lflang/generator/c/CCompiler.java

@@ -109,9 +109,9 @@ public boolean runCCompiler(GeneratorBase generator, LFGeneratorContext context)
     // avoid any error residue that can occur in CMake from
     // a previous build.
     // FIXME: This is slow and only needed if an error
-    //  has previously occurred. Deleting the build directory
-    //  if no prior errors have occurred can prolong the compilation
-    //  substantially. See #1416 for discussion.
+    // has previously occurred. Deleting the build directory
+    // if no prior errors have occurred can prolong the compilation
+    // substantially. See #1416 for discussion.
     FileUtil.deleteDirectory(buildPath);
     // Make sure the build directory exists
     Files.createDirectories(buildPath);
@@ -240,14 +240,15 @@ private static List<String> cmakeOptions(TargetConfig targetConfig, FileConfig f
                 + FileUtil.toUnixString(fileConfig.getOutPath().relativize(fileConfig.binPath)),
             "-DLF_FILE_SEPARATOR='" + quote + separator + quote + "'"));
     // Add #define for source file directory.
-    // Do not do this for federated programs because for those, the definition is put
-    // into the cmake file (and fileConfig.srcPath is the wrong directory anyway).
+    // Do not do this for federated programs because for those, the definition is
+    // put into the cmake file (and fileConfig.srcPath is the wrong directory
+    // anyway).
     if (!fileConfig.srcPath.toString().contains("fed-gen")) {
       // Do not convert to Unix path
       arguments.add("-DLF_SOURCE_DIRECTORY='" + quote + srcPath + quote + "'");
       arguments.add("-DLF_PACKAGE_DIRECTORY='" + quote + rootPath + quote + "'");
-      arguments.add("-DLF_SOURCE_GEN_DIRECTORY='" + quote + srcGenPath + quote + "'");
     }
+    arguments.add("-DLF_SOURCE_GEN_DIRECTORY='" + quote + srcGenPath + quote + "'");
     arguments.add(FileUtil.toUnixString(fileConfig.getSrcGenPath()));
 
     if (GeneratorUtils.isHostWindows()) {

core/src/main/java/org/lflang/validation/AttributeSpec.java

@@ -205,6 +205,8 @@ enum AttrParamType {
         new AttributeSpec(List.of(new AttrParamSpec(VALUE_ATTR, AttrParamType.STRING, false))));
     // @sparse
     ATTRIBUTE_SPECS_BY_NAME.put("sparse", new AttributeSpec(null));
+    // @transient
+    ATTRIBUTE_SPECS_BY_NAME.put("transient", new AttributeSpec(null));
     // @icon("value")
     ATTRIBUTE_SPECS_BY_NAME.put(
         "icon",

core/src/main/java/org/lflang/validation/LFValidator.java

@@ -531,6 +531,19 @@ public void checkInstantiation(Instantiation instantiation) {
         error("Variable-width banks are not supported.", Literals.INSTANTIATION__WIDTH_SPEC);
       }
     }
+
+    // If the Instantiation is annotated as '@transient', then:
+    // - The container has to be a federated reactor,
+    // - The coordination is centralized,
+    // - And the target is C.
+    if (AttributeUtils.isTransient(instantiation)) {
+      Reactor container = (Reactor) instantiation.eContainer();
+      if (!container.isFederated()) {
+        error(
+            "Only federates can be transients: " + instantiation.getReactorClass().getName(),
+            Literals.INSTANTIATION__REACTOR_CLASS);
+      }
+    }
   }
 
   @Check(CheckType.FAST)