Deduplicate generated parameters for TPE and Random (#4679)

nni/__init__.py

@@ -20,7 +20,7 @@ if dispatcher_env_vars.SDK_PROCESS != 'dispatcher':
     from .common.nas_utils import training_update
 
 class NoMoreTrialError(Exception):
-    def __init__(self, ErrorInfo):
+    def __init__(self, ErrorInfo='Search space fully explored'):
         super().__init__(self)
         self.errorinfo = ErrorInfo
 

nni/algorithms/hpo/gridsearch_tuner.py

@@ -200,13 +200,18 @@ class GridSearchTuner(Tuner):
                     mid = (l + r) / 2
                     diff_l = _less(l, mid, spec)
                     diff_r = _less(mid, r, spec)
-                    if diff_l and diff_r:  # we can skip these for non-q, but it will complicate the code
+                    # if l != 0 and r != 1, then they are already in the grid, else they are not
+                    # the special case is needed because for normal distribution 0 and 1 will generate infinity
+                    if (diff_l or l == 0.0) and (diff_r or r == 1.0):
+                        # we can skip these for non-q, but it will complicate the code
                         new_vals.append(mid)
                         updated = True
                     if diff_l:
                         new_divs.append((l, mid))
+                        updated = (updated or l == 0.0)
                     if diff_r:
                         new_divs.append((mid, r))
+                        updated = (updated or r == 1.0)
                 self.grid[i] += new_vals
                 self.divisions[i] = new_divs
 

nni/algorithms/hpo/random_tuner.py

@@ -17,7 +17,7 @@ import numpy as np
 import schema
 
 from nni import ClassArgsValidator
-from nni.common.hpo_utils import format_search_space, deformat_parameters
+from nni.common.hpo_utils import Deduplicator, format_search_space, deformat_parameters
 from nni.tuner import Tuner
 
 _logger = logging.getLogger('nni.tuner.random')
@@ -47,13 +47,16 @@ class RandomTuner(Tuner):
         if seed is None:  # explicitly generate a seed to make the experiment reproducible
             seed = np.random.default_rng().integers(2 ** 31)
         self.rng = np.random.default_rng(seed)
+        self.dedup = None
         _logger.info(f'Using random seed {seed}')
 
     def update_search_space(self, space):
         self.space = format_search_space(space)
+        self.dedup = Deduplicator(self.space)
 
     def generate_parameters(self, *args, **kwargs):
         params = suggest(self.rng, self.space)
+        params = self.dedup(params)
         return deformat_parameters(params, self.space)
 
     def receive_trial_result(self, *args, **kwargs):

nni/algorithms/hpo/tpe_tuner.py

@@ -23,7 +23,7 @@ from typing import Any, NamedTuple
 import numpy as np
 from scipy.special import erf  # pylint: disable=no-name-in-module
 
-from nni.common.hpo_utils import OptimizeMode, format_search_space, deformat_parameters, format_parameters
+from nni.common.hpo_utils import Deduplicator, OptimizeMode, format_search_space, deformat_parameters, format_parameters
 from nni.tuner import Tuner
 from nni.typehint import Literal
 from nni.utils import extract_scalar_reward
@@ -153,6 +153,7 @@ class TpeTuner(Tuner):
         # concurrent generate_parameters() calls are likely to yield similar result, because they use same history
         # the liar solves this problem by adding fake results to history
         self.liar = create_liar(self.args.constant_liar_type)
+        self.dedup = None
 
         if seed is None:  # explicitly generate a seed to make the experiment reproducible
             seed = np.random.default_rng().integers(2 ** 31)
@@ -165,6 +166,7 @@ class TpeTuner(Tuner):
 
     def update_search_space(self, space):
         self.space = format_search_space(space)
+        self.dedup = Deduplicator(self.space)
 
     def generate_parameters(self, parameter_id, **kwargs):
         if self.liar and self._running_params:
@@ -178,6 +180,7 @@ class TpeTuner(Tuner):
             history = self._history
 
         params = suggest(self.args, self.rng, self.space, history)
+        params = self.dedup(params)
 
         self._params[parameter_id] = params
         self._running_params[parameter_id] = params

nni/common/hpo_utils/__init__.py

 # Copyright (c) Microsoft Corporation.
 # Licensed under the MIT license.
 
+from .dedup import Deduplicator
 from .validation import validate_search_space
 from .formatting import *
 from .optimize_mode import OptimizeMode

nni/common/hpo_utils/dedup.py

+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT license.
+
+"""
+Deduplicate repeated parameters.
+
+No guarantee for forward-compatibility.
+"""
+
+import logging
+
+import nni
+from .formatting import deformat_parameters
+
+_logger = logging.getLogger(__name__)
+
+# TODO:
+# Move main logic of basic tuners (random and grid search) into SDK,
+# so we can get rid of private methods and circular dependency.
+
+class Deduplicator:
+    """
+    A helper for tuners to deduplicate generated parameters.
+
+    When the tuner generates an already existing parameter,
+    calling this will return a new parameter generated with grid search.
+    Otherwise it returns the orignial parameter object.
+
+    If all parameters have been generated, raise ``NoMoreTrialError``.
+
+    All search space types, including nested choice, are supported.
+
+    Resuming and updating search space are not supported for now.
+    It will not raise error, but may return duplicate parameters.
+
+    See random tuner's source code for example usage.
+    """
+
+    def __init__(self, formatted_search_space):
+        self._space = formatted_search_space
+        self._never_dup = any(_spec_never_dup(spec) for spec in self._space.values())
+        self._history = set()
+        self._grid_search = None
+
+    def __call__(self, formatted_parameters):
+        if self._never_dup or self._not_dup(formatted_parameters):
+            return formatted_parameters
+
+        if self._grid_search is None:
+            _logger.info(f'Tuning algorithm generated duplicate parameter: {formatted_parameters}')
+            _logger.info(f'Use grid search for deduplication.')
+            self._init_grid_search()
+
+        while True:
+            new = self._grid_search._suggest()
+            if new is None:
+                raise nni.NoMoreTrialError()
+            if self._not_dup(new):
+                return new
+
+    def _init_grid_search(self):
+        from nni.algorithms.hpo.gridsearch_tuner import GridSearchTuner
+        self._grid_search = GridSearchTuner()
+        self._grid_search.history = self._history
+        self._grid_search.space = self._space
+        self._grid_search._init_grid()
+
+    def _not_dup(self, formatted_parameters):
+        params = deformat_parameters(formatted_parameters, self._space)
+        params_str = nni.dump(params, sort_keys=True)
+        if params_str in self._history:
+            return False
+        else:
+            self._history.add(params_str)
+            return True
+
+def _spec_never_dup(spec):
+    if spec.is_nested():
+        return False  # "not chosen" duplicates with "not chosen"
+    if spec.categorical or spec.q is not None:
+        return False
+    if spec.normal_distributed:
+        return spec.sigma > 0
+    else:
+        return spec.low < spec.high

nni/common/hpo_utils/formatting.py

@@ -78,9 +78,16 @@ class ParameterSpec(NamedTuple):
         For nested search space, check whether this parameter should be skipped for current set of paremters.
         This function must be used in a pattern similar to random tuner. Otherwise it will misbehave.
         """
-        if len(self.key) < 2 or isinstance(self.key[-2], str):
-            return True
+        if self.is_nested():
             return partial_parameters[self.key[:-2]] == self.key[-2]
+        else:
+            return True
+
+    def is_nested(self):
+        """
+        Check whether this parameter is inside a nested choice.
+        """
+        return len(self.key) >= 2 and isinstance(self.key[-2], int)
 
 def format_search_space(search_space: SearchSpace) -> FormattedSearchSpace:
     """
@@ -88,10 +95,6 @@ def format_search_space(search_space: SearchSpace) -> FormattedSearchSpace:
     The dict key is dict value's `ParameterSpec.key`.
     """
     formatted = _format_search_space(tuple(), search_space)
-    # In CPython 3.6, dicts preserve order by internal implementation.
-    # In Python 3.7+, dicts preserve order by language spec.
-    # Python 3.6 is crappy enough. Don't bother to do extra work for it.
-    # Remove these comments when we drop 3.6 support.
     return {spec.key: spec for spec in formatted}
 
 def deformat_parameters(

test/ut/sdk/test_builtin_tuners.py

@@ -324,11 +324,13 @@ class BuiltinTunersTestCase(TestCase):
         self.import_data_test(tuner_fn, support_middle=False)
 
     def test_tpe(self):
+        self.exhaustive = True
         tuner_fn = TpeTuner
         self.search_space_test_all(TpeTuner)
         self.import_data_test(tuner_fn)
 
     def test_random_search(self):
+        self.exhaustive = True
         tuner_fn = RandomTuner
         self.search_space_test_all(tuner_fn)
         self.import_data_test(tuner_fn)

test/ut/sdk/test_hpo_dedup.py

+import numpy as np
+
+import nni
+from nni.algorithms.hpo.random_tuner import suggest
+from nni.common.hpo_utils import Deduplicator, deformat_parameters, format_search_space
+
+seed = np.random.default_rng().integers(2 ** 31)
+print(seed)
+rng = np.random.default_rng(seed)
+
+finite_space = {
+    'x': {'_type': 'choice', '_value': ['a', 'b']},
+    'y': {'_type': 'quniform', '_value': [0, 1, 0.6]},
+    'z': {'_type': 'normal', '_value': [1, 0]},
+}
+
+infinite_space = {
+    'x': {'_type': 'choice', '_value': ['a', 'b']},
+    'y': {'_type': 'uniform', '_value': [0, 1]},
+}
+
+nested_space = {
+    'outer': {
+        '_type': 'choice',
+        '_value': [
+            {'_name': 'A', 'x': {'_type': 'choice', '_value': ['a', 'b']}},
+            {'_name': 'B', 'y': {'_type': 'uniform', '_value': [0, 1]}},
+        ]
+    }
+}
+
+def test_dedup_finite():
+    space = format_search_space(finite_space)
+    dedup = Deduplicator(space)
+    params = []
+    exhausted = False
+    try:
+        for i in range(7):
+            p = dedup(suggest(rng, space))
+            params.append(deformat_parameters(p, space))
+    except nni.NoMoreTrialError:
+        exhausted = True
+    params = sorted(params, key=(lambda p: (p['x'], p['y'], p['z'])))
+    assert exhausted
+    assert params == [
+        {'x': 'a', 'y': 0.0, 'z': 1.0},
+        {'x': 'a', 'y': 0.6, 'z': 1.0},
+        {'x': 'a', 'y': 1.0, 'z': 1.0},
+        {'x': 'b', 'y': 0.0, 'z': 1.0},
+        {'x': 'b', 'y': 0.6, 'z': 1.0},
+        {'x': 'b', 'y': 1.0, 'z': 1.0},
+    ]
+
+def test_dedup_infinite():
+    space = format_search_space(infinite_space)
+    dedup = Deduplicator(space)
+    for i in range(10):
+        p = suggest(rng, space)
+        assert dedup(p) is p
+
+def test_dedup_nested():
+    space = format_search_space(nested_space)
+    dedup = Deduplicator(space)
+    params = set()
+    for i in range(10):
+        p = dedup(suggest(rng, space))
+        s = nni.dump(deformat_parameters(p, space), sort_keys=True)
+        assert s not in params
+        params.add(s)
+
+if __name__ == '__main__':
+    test_dedup_finite()
+    test_dedup_infinite()
+    test_dedup_nested()