Expose isReady to check if sync will block (#123 #22)

weave.nim

@@ -20,7 +20,7 @@ export
   parallelFor, parallelForStrided,
   init, exit,
   loadBalance,
-  isSpawned,
+  isSpawned, isReady,
   getThreadId, getNumThreads,
   # Experimental threadlocal prologue/epilogue
   parallelForStaged, parallelForStagedStrided,

weave/datatypes/flowvars.nim

@@ -83,9 +83,16 @@ EagerFV:
     let resultSent {.used.} = fv.chan[].trySend(childResult)
     postCondition: resultSent
 
-  template isFutReady*(fv: Flowvar): bool =
+  template tryComplete*[T](fv: Flowvar, parentResult: var T): bool =
     fv.chan[].tryRecv(parentResult)
 
+  func isReady*[T](fv: Flowvar[T]): bool {.inline.} =
+    ## Returns true if the result of a Flowvar is ready.
+    ## In that case `sync` will not block.
+    ## Otherwise the current will block to help on all the pending tasks
+    ## until the Flowvar is ready.
+    not fv.chan.isEmpty()
+
 LazyFV:
   proc recycleChannel*(fv: Flowvar) {.inline.} =
     recycle(fv.lfv.lazy.chan)
@@ -108,13 +115,23 @@ LazyFV:
       ascertain: not fv.lfv.lazy.chan.isNil
       discard fv.lfv.lazy.chan[].trySend(childResult)
 
-  template isFutReady*(fv: Flowvar): bool =
+  template tryComplete*[T](fv: Flowvar, parentResult: var T): bool =
     if fv.lfv.hasChannel:
       ascertain: not fv.lfv.lazy.chan.isNil
       fv.lfv.lazy.chan[].tryRecv(parentResult)
     else:
       fv.lfv.isReady
 
+  func isReady*[T](fv: Flowvar[T]): bool {.inline.} =
+    ## Returns true if the result of a Flowvar is ready.
+    ## In that case `sync` will not block.
+    ## Otherwise the current will block to help on all the pending tasks
+    ## until the Flowvar is ready.
+    if not fv.lfv.hasChannel:
+      fv.lfv.isReady
+    else:
+      not fv.lfv.lazy.chan.isEmpty()
+
   import sync_types
 
   proc convertLazyFlowvar*(task: Task) {.inline.}=

weave/state_machines/sync.dot

@@ -1,27 +1,27 @@
 digraph awaitFSA{
     splines=ortho;
     node [shape = doublecircle]; InitialState AW_Exit;
-    node [shape = circle, fontcolor=white, fillcolor=darkslategrey, style="filled"]; AW_Steal AW_SuccessfulTheft AW_CheckTask AW_OutOfChildTasks;
+    node [shape = circle, fontcolor=white, fillcolor=darkslategrey, style="filled"]; AW_Steal AW_SuccessfulTheft AW_CheckTask AW_OutOfDirectChildTasks;
     InitialState -> AW_CheckTask [color="black:invis:black", xlabel="entry point"];
     node [shape = octagon, fontcolor=black, fillcolor=lightsteelblue, style="rounded,filled"]; AW_Steal_AWE_ReceivedTask AW_CheckTask_AWE_HasChildTask ;
-    node [shape = diamond, fontcolor=black, fillcolor=coral, style="rounded,filled"]; AW_Steal_AWE_FutureReady AW_CheckTask_AWE_FutureReady AW_OutOfChildTasks_AWE_FutureReady ;
+    node [shape = diamond, fontcolor=black, fillcolor=coral, style="rounded,filled"]; AW_Steal_AWE_FutureReady AW_CheckTask_AWE_FutureReady AW_OutOfDirectChildTasks_AWE_FutureReady ;
     AW_Steal_AWE_ReceivedTask [label="AWE_ReceivedTask\nlootedTask"];
     AW_CheckTask_AWE_HasChildTask [label="AWE_HasChildTask\nnot task.isNil"];
-    AW_Steal_AWE_FutureReady [label="AWE_FutureReady\nisFutReady(fv)"];
-    AW_CheckTask_AWE_FutureReady [label="AWE_FutureReady\nisFutReady(fv)"];
-    AW_OutOfChildTasks_AWE_FutureReady [label="AWE_FutureReady\nisFutReady(fv)"];
+    AW_Steal_AWE_FutureReady [label="AWE_FutureReady\ntryComplete(fv, parentResult)"];
+    AW_CheckTask_AWE_FutureReady [label="AWE_FutureReady\ntryComplete(fv, parentResult)"];
+    AW_OutOfDirectChildTasks_AWE_FutureReady [label="AWE_FutureReady\ntryComplete(fv, parentResult)"];
     AW_Steal -> AW_Steal_AWE_FutureReady[style=bold, xlabel="always"];
     AW_Steal_AWE_FutureReady -> AW_Exit [color="coral", fontcolor="coral", xlabel="interrupted"];
     AW_Steal_AWE_FutureReady -> AW_Steal_AWE_ReceivedTask[xlabel="normal flow"];
     AW_Steal_AWE_ReceivedTask -> AW_SuccessfulTheft [style=dashed, xlabel="true"];
     AW_Steal_AWE_ReceivedTask -> AW_Steal [xlabel="default"];
-    AW_SuccessfulTheft -> AW_OutOfChildTasks [xlabel="default"];
+    AW_SuccessfulTheft -> AW_OutOfDirectChildTasks [xlabel="default"];
     AW_CheckTask -> AW_CheckTask_AWE_FutureReady[style=bold, xlabel="always"];
     AW_CheckTask_AWE_FutureReady -> AW_Exit [color="coral", fontcolor="coral", xlabel="interrupted"];
     AW_CheckTask_AWE_FutureReady -> AW_CheckTask_AWE_HasChildTask[xlabel="normal flow"];
     AW_CheckTask_AWE_HasChildTask -> AW_CheckTask [style=dashed, xlabel="true"];
-    AW_CheckTask_AWE_HasChildTask -> AW_OutOfChildTasks [xlabel="default"];
-    AW_OutOfChildTasks -> AW_OutOfChildTasks_AWE_FutureReady[style=bold, xlabel="always"];
-    AW_OutOfChildTasks_AWE_FutureReady -> AW_Exit [color="coral", fontcolor="coral", xlabel="interrupted"];
-    AW_OutOfChildTasks_AWE_FutureReady -> AW_Steal [xlabel="default"];
+    AW_CheckTask_AWE_HasChildTask -> AW_OutOfDirectChildTasks [xlabel="default"];
+    AW_OutOfDirectChildTasks -> AW_OutOfDirectChildTasks_AWE_FutureReady[style=bold, xlabel="always"];
+    AW_OutOfDirectChildTasks_AWE_FutureReady -> AW_Exit [color="coral", fontcolor="coral", xlabel="interrupted"];
+    AW_OutOfDirectChildTasks_AWE_FutureReady -> AW_Steal [xlabel="default"];
 }

weave/state_machines/sync.nim

@@ -48,7 +48,7 @@ setTerminalState(awaitFSA, AW_Exit)
 # -------------------------------------------
 
 implEvent(awaitFSA, AWE_FutureReady):
-  isFutReady(fv)
+  tryComplete(fv, parentResult)
 
 behavior(awaitFSA):
   # In AW_Steal we might recv tasks and steal requests which get stuck in our queues