cma.interfaces.OOOptimizer

Examples

All examples minimize the function elli, the output is not shown. (A preferred environment to execute all examples is ipython.)

First we need:

# CMAEvolutionStrategy derives from the OOOptimizer class
from cma import CMAEvolutionStrategy
from cma.fitness_functions import elli

The shortest example uses the inherited method OOOptimizer.optimize:

es = CMAEvolutionStrategy(8 * [0.1], 0.5).optimize(elli)

The input parameters to CMAEvolutionStrategy are specific to this inherited class. The remaining functionality is based on interface defined by OOOptimizer. We might have a look at the result:

print(es.result[0])  # best solution and
print(es.result[1])  # its function value

Virtually the same example can be written with an explicit loop instead of using optimize. This gives the necessary insight into the OOOptimizer class interface and entire control over the iteration loop:

# a new CMAEvolutionStrategy instance
optim = CMAEvolutionStrategy(9 * [0.5], 0.3)

# this loop resembles optimize()
while not optim.stop():  # iterate
    X = optim.ask()      # get candidate solutions
    f = [elli(x) for x in X]  # evaluate solutions
    #  in case do something else that needs to be done
    optim.tell(X, f)     # do all the real "update" work
    optim.disp(20)       # display info every 20th iteration
    optim.logger.add()   # log another "data line", non-standard

# final output
print('termination by', optim.stop())
print('best f-value =', optim.result[1])
print('best solution =', optim.result[0])
optim.logger.plot()  # if matplotlib is available

Details

Most of the work is done in the methods tell or ask. The property result provides more useful output.