Add a whole corpus sampler

This patch adds a whole corpus sampler. This is intended to be used for
trace data collection where we need to compile an entire corpus subset
that is extracted using separate tooling in order to generate a reward.

compiler_opt/rl/corpus.py

@@ -224,6 +224,24 @@ def __call__(self, k: int, n: int = 10) -> List[ModuleSpec]:
     return list(results)
 
 
+class WholeCorpusSampler(Sampler):
+  """Returns the entire corpus every time a sample is requested."""
+
+  def __init__(self, module_specs: Tuple[ModuleSpec]):
+    super().__init__(module_specs)
+
+  def reset(self):
+    pass
+
+  def __call__(self, k: int) -> List[ModuleSpec]:
+    """Returns the entire corpus a list of module specs."""
+    if len(self._module_specs) != k:
+      raise ValueError(
+          f'The number of modules requested {k} is not equal to '
+          f'the number of modules in the corpus, {len(self._module_specs)}')
+    return list(self._module_specs)
+
+
 class Corpus:
   """Represents a corpus.
 

compiler_opt/rl/corpus_test.py

@@ -267,6 +267,34 @@ def test_sample_without_replacement(self):
     self.assertEqual(samples[2].name, 'small')
     self.assertEqual(samples[3].name, 'smol')
 
+  def test_whole_corpus_sampler(self):
+    cps = corpus.create_corpus_for_testing(
+        location=self.create_tempdir(),
+        elements=[
+            corpus.ModuleSpec(name='xsmall', size=1),
+            corpus.ModuleSpec(name='small', size=5),
+            corpus.ModuleSpec(name='middle', size=20),
+            corpus.ModuleSpec(name='large', size=100)
+        ],
+        sampler_type=corpus.WholeCorpusSampler)
+    sample = cps.sample(4, sort=True)
+    self.assertLen(sample, 4)
+    self.assertEqual(sample[0].name, 'large')
+    self.assertEqual(sample[1].name, 'middle')
+    self.assertEqual(sample[2].name, 'small')
+    self.assertEqual(sample[3].name, 'xsmall')
+
+  def test_whole_corpus_sampler_invalid_count(self):
+    cps = corpus.create_corpus_for_testing(
+        location=self.create_tempdir(),
+        elements=[
+            corpus.ModuleSpec(name='small', size=1),
+            corpus.ModuleSpec(name='middle', size=2),
+        ],
+        sampler_type=corpus.WholeCorpusSampler)
+    with self.assertRaises(ValueError):
+      cps.sample(1)
+
   def test_filter(self):
     cps = corpus.create_corpus_for_testing(
         location=self.create_tempdir(),