Module gridworld

Generate random gridworld of given size.

While an instance of GridWorld is returned, other views of the result are possible; e.g., to obtain a description string, use GridWorld.dumps.

Parameters:

• size - a pair, indicating number of rows and columns.
• wall_density - the ratio of walls to total number of cells.
• num_init - number of possible initial positions.
• num_goals - number of positions to be visited infinitely often.
• prefix - string to be used as prefix for naming gridworld cell variables.
• num_trolls - number of random trolls to generate, each occupies an area of radius 1. If nonzero, then a list specifying the trolls will also be returned.
• ensure_feasible - guarantee that all goals and initial positions are mutually reachable, assuming a 4-connected grid. This method may not be complete, i.e., may fail to return a feasible random gridworld with the given parameters. Note that "feasibility" does not account for nondeterminism (in particular, nonzero num_trolls argument has no effect.)
• timeout - if ensure_feasible, then quit if no correct random world is found before timeout seconds. If timeout is None (default), then do not impose time constraints.

Returns: GridWorld, or None if timeout occurs.

Generate a narrow-passage world: this is a world containing two zones (initial, final) with a tube connecting them.

Parameters:

• size - a pair, indicating number of rows and columns.
• passage_width - the width of the connecting passage in cells.
• passage_length - the length of the passage as a proportion of the width of the world.
• num_init - number of possible initial positions.
• num_goals - number of positions to be visited infinitely often.
• ptop - row number of top of passage, default (None) is random
• prefix - string to be used as prefix for naming gridworld cell variables.

Returns: GridWorld

Generate entirely unoccupied gridworld of given size.

Parameters:

• size - a pair, indicating number of rows and columns.
• prefix - String to be used as prefix for naming gridworld cell variables.

Returns: GridWorld

Create GR(1) specification with troll-like obstacles.

Trolls are introduced into the specification with names derived from the given prefix and a number (matching the order in troll_list). Note that mutual exclusion is only between the controlled "Y gridworld" position and each troll, but not between trolls.

Parameters:

• Y (GridWorld) - The controlled gridworld, describing in particular static obstacles that must be respected by the trolls.
• troll_list - List of pairs of center position, to which the troll must always eventually return, and radius defining the extent of the trollspace. The radius is measured using infinity-norm.
• start_anywhere - If True, then initial troll position can be anywhere in its trollspace. Else (default), the troll is assumed to begin each game at its center position.
• nonbool - If True, then use variables with integer domains.
• get_moves_lists - Consult returned value description below.

Returns: (GRSpec, list)

If get_moves_lists is True, then returns (spec, moves_N) where spec is the specification incorporating all of the trolls, and moves_N is a list of lists of states (where "state" is given as a dictionary with keys of variable names), where the length of moves_N is equal to the number of trolls, and each element of moves_N is a list of possible states of that the corresponding troll (dynamic obstacle). If get_moves_lists is False, then moves_N is not returned and not computed.

Assuming prefix_R_C format, return (prefix,row,column) tuple.

prefix is of type string, row and column are integers.

The "nowhere" coordinate has form prefix_n_n. To indicate this, (-1, -1) is returned as the row, column position.

If error, return None or throw exception.

Animate a list of paths simultaneously in world Z using matplotlib.

Parameters:

• Z - Gridworld for which paths were generated.
• paths - List of paths to animate (one per robot). Each path is a list of pairs of gridworld cells, i.e., of the form [(r0, c0), (r1, c1), ...], where the first position is row r0 and column c0, etc.
• jitter - Random jitter added to each coordinate value in animation. Makes the robot's path more visible by avoiding overlap.
• save_prefix - If not None, do not show an animation but produce a series of images "<save_prefix>nnn.png" which can be compiled into an animated GIF.