Add function to calculate BOHB behavior

hpbandster/utils.py

@@ -1,58 +1,91 @@
 import os.path
 import json
-import threading
 
+import threading
+import numpy as np
 import Pyro4
 import Pyro4.naming
 
-
 from hpbandster.core.result import Result
 from hpbandster.core.base_iteration import Datum
 
 
-
 def nic_name_to_host(nic_name):
-	""" translates the name of a network card into a valid host name"""
-	from netifaces import ifaddresses, AF_INET
-	host = ifaddresses(nic_name).setdefault(AF_INET, [{'addr': 'No IP addr'}] )[0]['addr']
-	return(host)
-
+    """ translates the name of a network card into a valid host name"""
+    from netifaces import ifaddresses, AF_INET
+    host = ifaddresses(nic_name).setdefault(AF_INET, [{'addr': 'No IP addr'}])[0]['addr']
+    return (host)
 
 
 def start_local_nameserver(host=None, port=0, nic_name=None):
-	"""
-		starts a Pyro4 nameserver in a daemon thread
-
-		Parameters:
-		-----------
-			host: str
-				the hostname to use for the nameserver
-			port: int
-				the port to be used. Default =0 means a random port
-			nic_name: str
-				name of the network interface to use
-
-		Returns:
-		--------
-			tuple (str, int):
-				the host name and the used port
-	"""
-
-	if host is None:
-		if nic_name is None:
-			host = 'localhost'
-		else:
-			host = nic_name_to_host(nic_name)
-
-	uri, ns, _ = Pyro4.naming.startNS(host=host, port=port)
-	host, port = ns.locationStr.split(':')
-
-
-	thread = threading.Thread(target=ns.requestLoop, name='Pyro4 nameserver started by HpBandSter')
-	thread.daemon=True
-
-	thread.start()
-	return(host, int(port))
+    """
+        starts a Pyro4 nameserver in a daemon thread
+
+        Parameters:
+        -----------
+            host: str
+                the hostname to use for the nameserver
+            port: int
+                the port to be used. Default =0 means a random port
+            nic_name: str
+                name of the network interface to use
+
+        Returns:
+        --------
+            tuple (str, int):
+                the host name and the used port
+    """
+
+    if host is None:
+        if nic_name is None:
+            host = 'localhost'
+        else:
+            host = nic_name_to_host(nic_name)
+
+    uri, ns, _ = Pyro4.naming.startNS(host=host, port=port)
+    host, port = ns.locationStr.split(':')
+
+    thread = threading.Thread(target=ns.requestLoop, name='Pyro4 nameserver started by HpBandSter')
+    thread.daemon = True
+
+    thread.start()
+    return (host, int(port))
+
+
+def predict_bohb_run(min_budget, max_budget, eta, n_iterations):
+    """
+    Prints the expected numbers of configurations, runs and budgets given BOHB's hyperparameters.
+
+    Parameters
+    ----------
+    min_budget : float
+        The smallest budget to consider.
+    max_budget : float
+        The largest budget to consider.
+    eta : int
+        The eta parameter. Determines how many configurations advance to the next round.
+    n_iterations : int
+        How many iterations of SuccessiveHalving to perform.
+    """
+    s_max = -int(np.log(min_budget / max_budget) / np.log(eta)) + 1
+
+    n_runs = 0
+    n_configurations = []
+    initial_budgets = []
+    for iteration in range(n_iterations):
+        s = s_max - 1 - (iteration % s_max)
 
+        initial_budget = (eta ** -s) * max_budget
+        initial_budgets.append(initial_budget)
 
+        n0 = int(np.floor(s_max / (s + 1)) * eta ** s)
+        n_configurations.append(n0)
+        ns = [max(int(n0 * (eta ** (-i))), 1) for i in range(s + 1)]
+        n_runs += sum(ns)
 
+    print('Running BOHB with these parameters will proceed as follows:')
+    print('  {} iterations of SuccessiveHalving will be executed.'.format(n_iterations))
+    print('  The iterations will start with a number of configurations as {}.'.format(n_configurations))
+    print('  With the initial budgets as {}.'.format(initial_budgets))
+    print('  A total of {} unique configurations will be sampled.'.format(sum(n_configurations)))
+    print('  A total of {} runs will be executed.'.format(n_runs))

tests/test_utils.py

@@ -1,5 +1,7 @@
 import unittest
 import logging
+from io import StringIO
+import sys
 
 logging.basicConfig(level=logging.WARNING)
 
@@ -32,5 +34,19 @@ def test_local_nameserver_2(self):
         self.assertEqual(ns.host, '127.0.0.1')
         ns.shutdown()
 
+    def test_predict_bohb_run(self):
+        stdout = StringIO()
+        sys.stdout = stdout
+        utils.predict_bohb_run(1, 9, eta=3, n_iterations=5)
+        expected = """Running BOHB with these parameters will proceed as follows:
+  5 iterations of SuccessiveHalving will be executed.
+  The iterations will start with a number of configurations as [9, 3, 3, 9, 3].
+  With the initial budgets as [1.0, 3.0, 9, 1.0, 3.0].
+  A total of 27 unique configurations will be sampled.
+  A total of 37 runs will be executed.
+"""
+        self.assertEqual(stdout.getvalue(), expected)
+
+
 if __name__ == '__main__':
     unittest.main()