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A simple implementation of backwards induction for solving finite-horizon, finite-state stochastic dynamic programs.

Project description

A simple implementation of backwards induction for solving finite-horizon, finite-space stochastic dynamic programs.

Installation

stochasticdp is available on PyPI:

pip install stochasticdp

Usage

To initialize a stochastic dynamic program:

dp = StochasticDP(number_of_stages, states, decisions, minimize)

where

  • number_of_stages is an integer
  • states is a list
  • decisions is a list
  • minimize is a boolean

This results in a stochastic dynamic program with stages numbered 0, ..., number_of_stages - 1, and initializes the following dictionaries:

  • dp.probability, where dp.probability[m, n, t, x] is the probability of moving from state n to state m in stage t under decision x
  • dp.contribution, where dp.contribution[m, n, t, x] is the immediate contribution of resulting from moving from state n to state m in stage t under decision x
  • dp.boundary, where dp.boundary[n] is the boundary condition for the value-to-go function at state n

You only need to define probabilities and contributions for transitions that occur with positive probability.

You can use the following helper functions to populate these dictionaries:

# This sets dp.probability[m, n, t, x] = p and dp.contribution[m, n, t, x] = c
dp.add_transition(stage=t, from_state=n, decision=x, to_state=m, probability=p, contribution=c)

# This sets dp.boundary[n] = v
dp.boundary(state=n, value=v)

To solve the stochastic dynamic program:

value, policy = dp.solve()

where

  • value is a dictionary: value[t, n] is the value-to-go function at stage t and state n
  • policy is a dictionary: policy[t, n] is the set of optimizers of value[t, n]

Project details


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Filename, size & hash SHA256 hash help File type Python version Upload date
stochasticdp-0.4.tar.gz (4.1 kB) Copy SHA256 hash SHA256 Source None Apr 10, 2018

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