Merge pull request #316 from lf-lang/decentralized-coord

Blog post on decentralized consistency

Author: edwardalee

blog/2025-10-14-decentralized-consistency.md

@@ -6,7 +6,7 @@ target C {
 import Count, Print from "Federated.lf"
 
 reactor PrintTimer extends Print {
-  timer t(0, 1 sec)
+  timer t(10 ms, 1 sec)
 
   reaction(t) {=
     lf_print("Timer ticked at (%lld, %d).",
@@ -18,5 +18,5 @@ reactor PrintTimer extends Print {
 federated reactor {
   c = new Count()
   p = new PrintTimer()
-  c.out -> p.in after 10 msec
+  c.out -> p.in after 10 ms
 }

docs/assets/code/c/src/DecentralizedTimerAfter.lf

@@ -13,7 +13,7 @@ reactor PrintTimer {
     lf_print("Received: %d at (%lld, %d)", in->value,
         lf_time_logical_elapsed(), lf_tag().microstep
     );
-  =} STAA(0) {=
+  =} tardy {=
     lf_print("****** Violation handler invoked at (%lld, %d). "
         "Intended tag was (%lld, %d).",
         lf_time_logical_elapsed(), lf_tag().microstep,
@@ -30,6 +30,7 @@ reactor PrintTimer {
 
 federated reactor {
   c = new Count()
+  @maxwait(10 ms)
   p = new PrintTimer()
-  c.out -> p.in after 10 msec
+  c.out -> p.in
 }

docs/assets/code/c/src/DecentralizedTimerAfterHandler.lf renamed to docs/assets/code/c/src/DecentralizedTimerHandler.lf

@@ -5,7 +5,7 @@ target C {
 
 import Count, Print from "Federated.lf"
 
-reactor PrintTimer(STA: time = 10 ms) extends Print {
+reactor PrintTimer extends Print {
   timer t(0, 1 sec)
 
   reaction(t) {=
@@ -17,6 +17,7 @@ reactor PrintTimer(STA: time = 10 ms) extends Print {
 
 federated reactor {
   c = new Count()
+  @maxwait(10 ms)
   p = new PrintTimer()
   c.out -> p.in
 }

docs/assets/code/c/src/DecentralizedTimerSTA.lf

@@ -1,4 +1,5 @@
 target C {
+  timeout: 3 s,
   coordination: decentralized
 }
 
@@ -16,14 +17,14 @@ reactor CountPrint {
     lf_print("***** CountPrint Received: %d at tag (%lld, %u)",
         in->value, lf_time_logical_elapsed(), lf_tag().microstep
     );
-  =} STAA(forever) {=
-    // This should never happen, but it is here to demonstrate the STAA violation handler.
-    lf_print_warning("CountPrint: Safe to process violation!");
+  =} tardy {=
+    // This should never happen, but it is here to demonstrate the tardy violation handler.
+    lf_print_warning("CountPrint: Message is tardy!");
     lf_print("Intended time: %lld", in->intended_tag.time - lf_time_start());
   =}
 }
 
-reactor Double(STA: time = forever) {
+reactor Double {
   input in: int
   output out: int
 
@@ -36,5 +37,6 @@ federated reactor {
   c = new CountPrint()
   p = new Double()
   c.out -> p.in
+  @absent_after(forever)
   p.out -> c.in
 }

docs/assets/code/c/src/DecentralizedFeedbackSTAA.lf renamed to docs/assets/code/c/src/DecentralizedZeroDelayLoop.lf

@@ -0,0 +1,28 @@
+target C {
+  timeout: 3 s,
+  coordination: decentralized
+}
+
+import CountPrint, Double from "DecentralizedZeroDelayLoop.lf"
+reactor CountPrintWithChecker extends CountPrint {
+
+  reaction(t, in) {=
+    if (!in->is_present) {
+      lf_print("***** CountPrint Failed to Receive response at tag (%lld, %u)",
+          lf_time_logical_elapsed(), lf_tag().microstep
+      );
+    }
+  =} tardy {=
+    lf_print("***** CountPrint Received tardy input: %d at tag (%lld, %u)",
+        in->value, lf_time_logical_elapsed(), lf_tag().microstep
+    );
+  =}
+}
+
+federated reactor {
+  c = new CountPrintWithChecker()
+  p = new Double()
+  c.out -> p.in
+  @absent_after(20 ms)
+  p.out -> c.in
+}

docs/assets/code/c/src/DecentralizedZeroDelayLoopWithChecker.lf

@@ -6,7 +6,7 @@ target Python {
 import Count, Print from "Federated.lf"
 
 reactor PrintTimer extends Print {
-  timer t(0, 1 sec)
+  timer t(10 ms, 1 sec)
 
   reaction(t) {=
     print(
@@ -19,5 +19,5 @@ reactor PrintTimer extends Print {
 federated reactor {
   c = new Count()
   p = new PrintTimer()
-  c.out -> p.inp after 10 msec
+  c.out -> p.inp after 10 ms
 }

docs/assets/code/py/src/DecentralizedTimerAfter.lf

@@ -14,7 +14,7 @@ reactor PrintTimer {
         f"Received: {inp.value} "
         f"at ({lf.time.logical_elapsed()}, {lf.tag().microstep})"
     )
-  =} STAA(0) {=
+  =} tardy {=
     print(
         "****** Violation handler invoked at "
         f"({lf.time.logical_elapsed()}, {lf.tag().microstep}). "
@@ -33,6 +33,7 @@ reactor PrintTimer {
 
 federated reactor {
   c = new Count()
+  @maxwait(10 ms)
   p = new PrintTimer()
-  c.out -> p.inp after 10 msec
+  c.out -> p.inp
 }

docs/assets/code/py/src/DecentralizedTimerAfterHandler.lf renamed to docs/assets/code/py/src/DecentralizedTimerHandler.lf

@@ -5,7 +5,7 @@ target Python {
 
 import Count, Print from "Federated.lf"
 
-reactor PrintTimer(STA = 10 ms) extends Print {
+reactor PrintTimer extends Print {
   timer t(0, 1 sec)
 
   reaction(t) {=
@@ -18,6 +18,7 @@ reactor PrintTimer(STA = 10 ms) extends Print {
 
 federated reactor {
   c = new Count()
+  @maxwait(10 ms)
   p = new PrintTimer()
   c.out -> p.inp
 }

docs/assets/code/py/src/DecentralizedTimerSTA.lf

@@ -1,4 +1,5 @@
 target Python {
+  timeout: 3 s,
   coordination: decentralized
 }
 
@@ -15,14 +16,14 @@ reactor CountPrint {
 
   reaction(inp) {=
     print(f"***** CountPrint Received: {inp.value} at tag ({lf.time.logical_elapsed()}, {lf.tag().microstep})")
-  =} STAA(forever) {=
+  =} tardy {=
     # This should never happen, but it is here to demonstrate the STAA violation handler.
     print("CountPrint: Safe to process violation!")
     print(f"Intended time: {inp.intended_tag.time - lf.time.start()}")
   =}
 }
 
-reactor Double(STA = forever) {
+reactor Double {
   input inp
   output out
 
@@ -35,5 +36,6 @@ federated reactor {
   c = new CountPrint()
   p = new Double()
   c.out -> p.inp
+  @absent_after(forever)
   p.out -> c.inp
 }