Replace pract6.c

D4-MPI/01-MPI-P2P/exercise/pract6.c

@@ -3,6 +3,10 @@
 
 int main(int argc, char **argv){
 
+/*
+ * Compile with
+ * mpiicc -o prog pract6.c
+*/
 
 /*
  * Construct a MPI program that has two ranks.