Add max_resample option in Hill Estimator to avoid infinite loop

[mu373]

Overview

• Fixed a bug where Hill Estimator gets infinite loop during resampling. Infinite (?) loop when fitting HillEstimator #35
• It was caused by if k2 > k1 condition in hill_dbs(). For n<200, int(0.005*n) always floors to 0, which does not increment min_index1 and min_index2. This results in k1 and k2 to be stuck causing the infinite loop.

if k2 > k1:
    print("Warning (Hill): k2 > k1, AMSE false minimum suspected, resampling...")
    # move left AMSE boundary to avoid numerical issues
    min_index1 = min_index1 + int(0.005*n)
    min_index2 = min_index2 + int(0.005*n)
    k2 = None

Changes

• Added max_resample option in Hill Estimator. If resampling count exceeds this, it raises RuntimeError.

HillEstimator(bootstrap=True, max_resample=3)

• Added tests for max_resample with provided degree sequence.