From c7f99fa201f4aac01db65bfe1469801f48ea0f9a Mon Sep 17 00:00:00 2001
From: Eddie Pantridge <EPantridge@MassMutual.com>
Date: Fri, 2 Sep 2016 23:10:02 -0400
Subject: [PATCH] Fixed bug in automatic epsilon lexicase, and added example.

---
 deap/tools/selection.py                 |  4 +-
 examples/gp/symbreg_epsilon_lexicase.py | 92 +++++++++++++++++++++++++
 2 files changed, 94 insertions(+), 2 deletions(-)
 create mode 100644 examples/gp/symbreg_epsilon_lexicase.py

diff --git a/deap/tools/selection.py b/deap/tools/selection.py
index a83525b6a..d69e168ed 100644
--- a/deap/tools/selection.py
+++ b/deap/tools/selection.py
@@ -295,9 +295,9 @@ def selAutomaticEpsilonLexicase(individuals, k):
         random.shuffle(cases)
 
         while len(cases) > 0 and len(candidates) > 1: 
-            errors_for_this_case = [x.fitness.values[cases[0] for x in candidates]
+            errors_for_this_case = [x.fitness.values[cases[0]] for x in candidates]
             median_val = np.median(errors_for_this_case)
-            median_absolute_deviation = np.median([abs(x - median_val) for x in candidates])
+            median_absolute_deviation = np.median([abs(x - median_val) for x in errors_for_this_case])
             if fit_weights[cases[0]] > 0:
                 best_val_for_case = max(errors_for_this_case) 
                 min_val_to_survive = best_val_for_case - median_absolute_deviation
diff --git a/examples/gp/symbreg_epsilon_lexicase.py b/examples/gp/symbreg_epsilon_lexicase.py
new file mode 100644
index 000000000..86a993faa
--- /dev/null
+++ b/examples/gp/symbreg_epsilon_lexicase.py
@@ -0,0 +1,92 @@
+#    This file is part of EAP.
+#
+#    EAP is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU Lesser General Public License as
+#    published by the Free Software Foundation, either version 3 of
+#    the License, or (at your option) any later version.
+#
+#    EAP is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+#    GNU Lesser General Public License for more details.
+#
+#    You should have received a copy of the GNU Lesser General Public
+#    License along with EAP. If not, see <http://www.gnu.org/licenses/>.
+
+import operator
+import math
+import random
+
+import numpy
+
+from deap import algorithms
+from deap import base
+from deap import creator
+from deap import tools
+from deap import gp
+
+# Define new functions
+def protectedDiv(left, right):
+    try:
+        return left / right
+    except ZeroDivisionError:
+        return 1
+
+pset = gp.PrimitiveSet("MAIN", 1)
+pset.addPrimitive(operator.add, 2)
+pset.addPrimitive(operator.sub, 2)
+pset.addPrimitive(operator.mul, 2)
+pset.addPrimitive(protectedDiv, 2)
+pset.addPrimitive(operator.neg, 1)
+pset.addPrimitive(math.cos, 1)
+pset.addPrimitive(math.sin, 1)
+pset.addEphemeralConstant("rand101", lambda: random.randint(-1,1))
+pset.renameArguments(ARG0='x')
+
+creator.create("FitnessMin", base.Fitness, weights=(-1.0,))
+creator.create("Individual", gp.PrimitiveTree, fitness=creator.FitnessMin)
+
+toolbox = base.Toolbox()
+toolbox.register("expr", gp.genHalfAndHalf, pset=pset, min_=1, max_=2)
+toolbox.register("individual", tools.initIterate, creator.Individual, toolbox.expr)
+toolbox.register("population", tools.initRepeat, list, toolbox.individual)
+toolbox.register("compile", gp.compile, pset=pset)
+
+def evalSymbReg(individual, points):
+    # Transform the tree expression in a callable function
+    func = toolbox.compile(expr=individual)
+    # Evaluate the mean squared error between the expression
+    # and the real function : x**4 + x**3 + x**2 + x
+    sqerrors = ((func(x) - x**4 - x**3 - x**2 - x)**2 for x in points)
+    return math.fsum(sqerrors) / len(points),
+
+toolbox.register("evaluate", evalSymbReg, points=[x/10. for x in range(-10,10)])
+toolbox.register("select", tools.selAutomaticEpsilonLexicase)
+toolbox.register("mate", gp.cxOnePoint)
+toolbox.register("expr_mut", gp.genFull, min_=0, max_=2)
+toolbox.register("mutate", gp.mutUniform, expr=toolbox.expr_mut, pset=pset)
+
+toolbox.decorate("mate", gp.staticLimit(key=operator.attrgetter("height"), max_value=17))
+toolbox.decorate("mutate", gp.staticLimit(key=operator.attrgetter("height"), max_value=17))
+
+def main():
+    #random.seed(318)
+
+    pop = toolbox.population(n=300)
+    hof = tools.HallOfFame(1)
+    
+    stats_fit = tools.Statistics(lambda ind: ind.fitness.values)
+    stats_size = tools.Statistics(len)
+    mstats = tools.MultiStatistics(fitness=stats_fit, size=stats_size)
+    mstats.register("avg", numpy.mean)
+    mstats.register("std", numpy.std)
+    mstats.register("min", numpy.min)
+    mstats.register("max", numpy.max)
+
+    pop, log = algorithms.eaSimple(pop, toolbox, 0.5, 0.1, 40, stats=mstats,
+                                   halloffame=hof, verbose=True)
+    # print log
+    return pop, log, hof
+
+if __name__ == "__main__":
+    main()