Changes between Version 66 and Version 67 of Next-GenOpenMPTransformation

Timestamp:

03/12/21 18:26:37 (5 years ago)

Author:

wuwenhao

Comment:

--

Next-GenOpenMPTransformation

@@ -11 +11 @@
     (Note that it only clean whats in between a pair of right mover and left mover.)
 3. A barrier is transformed as: barrier() ; check(); clean_all(); barrier();
+4. In a $track{..} scope, both read and write operations of shared variables are tracked for checking data race.
+    ($tracked_reads() and $tracked_writes() are functions returning a set containing all shared variables read or written.)
 
 E.g.,
@@ -19 +21 @@
   #pragma omp critical(c)
   {
-  B;
+    B;
   }
   C;
@@ -28 +30 @@
 
 {{{
-$depends_on(/*nothing*/)$atomic{
-  $track(&rs0, &ws0){  // SetStack: S0
-  A;
-  $yield;
-  $track(&rs1, &ws1){  // SetStack: S0, S1
-  E;
-  {
-    B;
-  }
-  X;
-  $check; // All var. in sets in SetStack
-  }       // clean S1 -- var. in B
-  C;
-  $check; 
-  }
-}
-}}}
-
+// Init parallel region env.
+$range _omp_thread_range = 0 .. _omp_nthreads - 1;
+$domain(1) _omp_dom = ($domain){_omp_thread_range};
+$omp_gteam _omp_gteam = $omp_gteam_create($here, _omp_nthreads);
+$for (int _omp_tid: _omp_dom) {
+  $depends_on(/*nothing*/)$atomic{
+    $omp_team _omp_team = $omp_team_create($here, _omp_gteam, _omp_tid);
+    $track{ // RS stack: rs0; WS stack: ws0;
+      // Enter parallel region
+      A; 
+      $yield();
+      $track{ // RS stack: rs0, rs1; WS stack: ws0, ws1;
+        $when(_omp_critical_c->value == 0);
+        $track{ // Ignore race on lock
+           _omp_critical_c->value = 1; // Enter critical block
+        }
+        B;
+        $track{ // Ignore race on lock
+           _omp_critical_c->value = 1; // Exit critical block
+        }
+        $check_data_race(); // 1st check
+      } // RS stack: rs0; WS stack: ws0; empty sets rs1, ws1;
+      C;
+      $check_data_race(); // 2nd check
+    } // RS stack: <empty>; WS stack: <empty>; empty sets rs0, ws0;
+  } // end $atomic
+} // end $for
+}}}
+
+We denotes Ax as thread x executes statement A. 
+Assuming there are two threads t0 and t1, 
+the first $check_data_race()  checks races between:
+
+A0,A1; A0,B1;  A1,B0; B0,C1; B1,C0;
+
+Then, the second $check_data_race() checks races between:
+
+A0,C1; A1,C0; C0,C1;
+
+Races between B0 and B1 are disabled, because B is in critical block.