Remove ambiguity warning from the scheduler

doc/tutorial.rst

@@ -456,8 +456,8 @@ control is the nesting of loops. For example, should the *i* loop be nested
 around the *j* loop, or the other way around, in the following simple
 zero-fill kernel?
 
-It turns out that Loopy will typically choose a loop nesting for us, but it
-does not like doing so. Loo.py will react to the following code
+It turns out that Loopy will choose a loop nesting for us, but it might be
+ambiguous. Consider the following code:
 
 .. doctest::
 
@@ -467,13 +467,8 @@ does not like doing so. Loo.py will react to the following code
     ...     a[i,j] = 0
     ...     """)
 
-By saying::
-
-    LoopyWarning: kernel scheduling was ambiguous--more than one schedule found, ignoring
-
-And by picking one of the possible loop orderings at random.
-
-The warning (and the nondeterminism it warns about) is easily resolved:
+Both nestings of the inames `i` and `j` result in a correct kernel.
+This ambiguity can be resolved:
 
 .. doctest::
 

loopy/schedule/__init__.py

@@ -1763,8 +1763,7 @@ def generate_loop_schedules(kernel, debug_args={}):
     new_limit = max(rec_limit, len(kernel.instructions) * 2)
     sys.setrecursionlimit(new_limit)
     try:
-        for sched in generate_loop_schedules_inner(kernel, debug_args=debug_args):
-            yield sched
+        return generate_loop_schedules_inner(kernel, debug_args=debug_args)
     finally:
         sys.setrecursionlimit(rec_limit)
 
@@ -1916,7 +1915,7 @@ def generate_loop_schedules_inner(kernel, debug_args={}):
 
                 from loopy.schedule.tools import add_extra_args_to_schedule
                 new_kernel = add_extra_args_to_schedule(new_kernel)
-                yield new_kernel
+                return new_kernel
 
                 debug.start()
 
@@ -1959,7 +1958,7 @@ def get_one_scheduled_kernel(kernel):
 
     if CACHING_ENABLED:
         try:
-            result, ambiguous = schedule_cache[sched_cache_key]
+            result = schedule_cache[sched_cache_key]
 
             logger.debug("%s: schedule cache hit" % kernel.name)
             from_cache = True
@@ -1967,38 +1966,18 @@ def get_one_scheduled_kernel(kernel):
             pass
 
     if not from_cache:
-        ambiguous = False
-
-        kernel_count = 0
-
         from time import time
         start_time = time()
 
         logger.info("%s: schedule start" % kernel.name)
 
-        for scheduled_kernel in generate_loop_schedules(kernel):
-            kernel_count += 1
-
-            if kernel_count == 1:
-                # use the first schedule
-                result = scheduled_kernel
-
-            if kernel_count == 2:
-                ambiguous = True
-                break
+        result = generate_loop_schedules(kernel)
 
         logger.info("%s: scheduling done after %.2f s" % (
             kernel.name, time()-start_time))
 
-    if ambiguous:
-        from warnings import warn
-        from loopy.diagnostic import LoopyWarning
-        warn("scheduling for kernel '%s' was ambiguous--more than one "
-                "schedule found, ignoring" % kernel.name, LoopyWarning,
-                stacklevel=2)
-
     if CACHING_ENABLED and not from_cache:
-        schedule_cache[sched_cache_key] = result, ambiguous
+        schedule_cache[sched_cache_key] = result
 
     return result