程序代写｜Project1 – Search 2
In this project, your Pacman agent will find paths through his maze world, both to reach a particular location and to collect food efficiently. You will build general search algorithms and apply them to Pacman scenarios.
Python Version: We will be using python3 for all programming projects including Project 0. Please install the latest version of python (python 3.xxx), if you have not already done that. Note that all of the progamming projects (Project 0, Project 1, Project 2, and Project 3) will not run using an older version of python (e.g., python2.xxx). Older versions of python are no longer supported. If you have multiple versions of python or you can’t see the GUI of the Pacman game, replace “python” with “python3” in all commands.
As in Project 0, this project includes an autograder for you to grade your answers on your machine. This can be run with the command:
See the autograder description in Project 0 for more information about using the autograder. The code for this project consists of several Python files, some of which you will need to read and understand in order to complete the assignment and some of which you can ignore. You can download all the code and supporting files from here.
Files you’ll edit:
Files you might want to look at:
Supporting files you can ignore:
Files to Edit and Submit: You will fill in portions of
searchAgents.py during the assignment. Once you have completed the assignment, you will submit
searchAgents.py in gradescope. Please do not change the other files in this distribution or submit any of our original files other than these files.
Evaluation: Your code will be autograded for technical correctness. Please do not change the names of any provided functions or classes within the code, or you will wreak havoc on the autograder. However, the correctness of your implementation – not the autograder’s judgements – will be the final judge of your score. If necessary, we will review and grade assignments individually to ensure that you receive due credit for your work.
Academic Dishonesty: We will be checking your code against other submissions in the class for logical redundancy. If you copy someone else’s code and submit it with minor changes, we will know. These cheat detectors are quite hard to fool, so please don’t try. We trust you all to submit your own work only; please don’t let us down. If you do, we will pursue the strongest consequences available to us.
Getting Help: You are not alone! If you find yourself stuck on something, post your questions on Piazza for help. Office hours are there for your support; please use them. If you can’t make our office hours, let us know and we will schedule an appointment for you. We want these projects to be rewarding and instructional, not frustrating and demoralizing. But, we don’t know when or how to help unless you ask.
Discussion: Please be careful not to post spoilers.
After downloading the code (search.zip), unzipping it, and changing to the directory, you should be able to play a game of Pacman by typing the following at the command line:
Pacman lives in a shiny blue world of twisting corridors and tasty round treats. Navigating this world efficiently will be Pacman’s first step in mastering his domain.
The simplest agent in
searchAgents.py is called the
GoWestAgent, which always goes West (a trivial reflex agent). This agent can occasionally win:
python pacman.py --layout testMaze --pacman GoWestAgent
But, things get ugly for this agent when turning is required:
python pacman.py --layout tinyMaze --pacman GoWestAgent
If Pacman gets stuck, you can exit the game by typing CTRL-c into your terminal.
Soon, your agent will solve not only
tinyMaze, but any maze you want.
pacman.py supports a number of options that can each be expressed in a long way (e.g.,
--layout) or a short way (e.g.,
-l). You can see the list of all options and their default values via:
python pacman.py -h
Also, all of the commands that appear in this project also appear in
commands.txt, for easy copying and pasting. In UNIX/Mac OS X, you can even run all these commands in order with
For the search algorithm implementations in q1-3, you will implement the following roughly-written pseudocode for graph search:
searchAgents.py, you’ll find a fully implemented
SearchAgent, which plans out a path through Pacman’s world and then executes that path step-by-step. The search algorithms for formulating a plan are not implemented – that’s your job.
First, test that the
SearchAgent is working correctly by running:
python pacman.py -l tinyMaze -p SearchAgent -a fn=tinyMazeSearch
The command above tells the
SearchAgent to use
tinyMazeSearch as its search algorithm, which is implemented in
search.py. Pacman should navigate the maze successfully.
Now it’s time to write full-fledged generic search functions to help Pacman plan routes! Pseudocode for the search algorithms you’ll write can be found in the lecture slides. Remember that a search node must contain not only a state but also the information necessary to reconstruct the path (plan) which gets to that state.
Important note: All of your search functions need to return a list of actions that will lead the agent from the start to the goal. These actions all have to be legal moves (valid directions, no moving through walls).
Important note: Make sure to use the
PriorityQueue data structures provided to you in
util.py! These data structure implementations have particular properties which are required for compatibility with the autograder.
Hint: Each algorithm is very similar. Algorithms for DFS, BFS, UCS, and A* differ only in the details of how the fringe is managed. So, concentrate on getting DFS right and the rest should be relatively straightforward. Indeed, one possible implementation requires only a single generic search method which is configured with an algorithm-specific queuing strategy. (Your implementation need not be of this form to receive full credit).
Implement the depth-first search (DFS) algorithm in the
depthFirstSearch function in
search.py. To make your algorithm complete, write the graph search version of DFS, which avoids expanding any already visited states. Your code should quickly find a solution for:
python pacman.py -l tinyMaze -p SearchAgent
python pacman.py -l mediumMaze -p SearchAgent
python pacman.py -l bigMaze -z .5 -p SearchAgent
The Pacman board will show an overlay of the states explored, and the order in which they were explored (brighter red means earlier exploration). Is the exploration order what you would have expected? Does Pacman actually go to all the explored squares on his way to the goal?
Hint: If you use a
Stack as your data structure, the solution found by your DFS algorithm for
mediumMaze should have a length of 130 (provided you push successors onto the fringe in the order provided by getSuccessors; you might get 246 if you push them in the reverse order). Is this a least-cost solution? If not, think about what depth-first search is doing wrong.
Grading: Please run the below command to see if your implementation passes all the autograder test cases:
python autograder.py -q q1
Implement the breadth-first search (BFS) algorithm in the
breadthFirstSearch function in
search.py. Again, write a graph search algorithm that avoids expanding any already visited states. Test your code the same way you did for the depth-first search.
python pacman.py -l mediumMaze -p SearchAgent -a fn=bfs
python pacman.py -l bigMaze -p SearchAgent -a fn=bfs -z .5
Does BFS find a least-cost solution? If not, check your implementation.
Hint: If Pacman moves too slowly for you, try the option
Note: If you’ve written your search code generically, your code should work equally well for the eight-puzzle search problem without any changes.
Grading: Please run the below command to see if your implementation passes all the autograder test cases.
python autograder.py -q q2