Restricted sampler is very sensitive to step-size damping

[nikohansen]

import cma
from cma import restricted_gaussian_sampler as rgs
cma.sigma_adaptation.CSA_dampfac_mueff = 2  # assure current setting
cma.sigma_adaptation.CSA_dampfac_mueff_inner = 1  # assure current setting

for damp in [1, 1.2]:
    es = cma.CMAEvolutionStrategy(20 * [1], 1,
            rgs.GaussVDSampler.extend_cma_options({
                'CSA_dampfac': damp,
                'seed': 6,
                'ftarget': 1e-8,
        }))
    es = es.optimize(cma.fitness_transformations.Rotated(cma.ff.cigar, seed=6), iterations=None, verb_disp=0)
    print('damping = {}'.format(es.adapt_sigma.damps))
    es.plot();