Project 2: Hash Analysis

Educational Objectives: After completing this assignment, the student should be able to accomplish the following:

• Describe and explain in detail the concept of hash table
• Implement hash tables as vector of lists
• Define and implement the ADT Table using a private hash table structure
• Define and implement bidirectional iterator class for this implementation of Table
• Calculate the theoretical bucket size distribution for Simple Uniform Hashing and a given table size
• Calculate the actual bucket size distribution for a given instance of a hash table
• Add methods to fsu::HashTable performing these calculations

Operational Objectives: Add two methods to the class template HashTable<K,T,H>:

size_t  HashTable<K,T,H>::MaxBucketSize () const;
void    HashTable<K,T,H>::Analysis      (std::ostream& os) const;

conforming to the requirements and specifications given below.

Deliverables: One file:

hashtbl.cpp  # contains implementations MaxBucketSize and Analysis

Note this is a slave file for hashtbl.h.

Procedural Requirements

1. The official development, testing, and assessment environment is gnu g++ on the linprog machines. Code should compile without error or warning, when all warning flags are set.

2. Begin by copying the following files from the course directory into your proj2 directory:

   LIB/proj2/hashtbl-stub.cpp      # slave file - stubbed versions of Analysis and MaxBucketSize
   LIB/proj2/makefile              # builds most executables
   LIB/proj2/proj2submit.sh        # submit script
   LIB/tcpp/hashtbl.h              # HashTable<> and HashTableIterator<>, except Analysis and MaxBucketSize
   LIB/tests/fhtbl.cpp             # test harness for hash tables
   LIB/tests/hashcalc.cpp          # calculates hash values interactively
   LIB/tests/hasheval.cpp          # test focusing specifically on Analysis
   LIB/tests/rantable.cpp          # creates random  table data 
   LIB/area51/fhtbl_i.x            # linprog/Intel/Linux executables
   LIB/area51/fhtblSimple_i.x
   LIB/area51/rantable_i.x
   LIB/area51/hashcalc_i.x
   LIB/area51/hashevalKISS_i.x
   LIB/area51/hashevalMM_i.x
   LIB/area51/hashevalSimple_i.x
   

   The executables in area51 are distributed only for your information and experimentation. You have the source code for these (except for hashtbl.cpp) and can build these to test your own code.

   The file hashtbl.h is copied ONLY FOR YOUR CONVENIENCE. Note this file is NOT submitted to your portfolio, so any code you write must deal with this file as it currently exists in the course library at the time. It is a good idea to rename this to "hashtbl.header" just to ensure that your code is reading the file from the library.

3. Your file hashtbl.cpp should contain implementations of Analysis and MaxBucketSize.

4. Copy the file proj2submit.sh into your project directory, change its permissions to executable, and submit the project by executing the script.

   Warning: Submit scripts do not work on the program and linprog servers. Use shell.cs.fsu.edu to submit projects. If you do not receive the second confirmation with the contents of your project, there has been a malfunction.

Code Requirements and Specifications - MaxBucketSize and Analysis

1. MaxBucketSize should return the size of the largest bucket in the hash table instance.

2. Analysis should result in a display (to the std::ostream passed in) as follows:

         table size:           9997
         number of buckets:    9973
           nonempty buckets:   6326
           max bucket size:    7
         expected search time: 2.00
           actual search time: 2.58
   
   bucket size distributions
   -------------------------
         size       actual         theory (uniform random distribution)
         ----       ------         ------
            0         3647         3659.9
            1         3685         3669.0
            2         1846         1838.9
            3          608          614.4
            4          145          153.9
            5           37           30.9
            6            4            5.2
            7            1            0.7
            8                         0.1
   

   This display shows the size of the table, number of buckets, number of non-empty buckets, max bucket size, expected search time [1 + (table size)/(number of buckets)], actual average search time [1 + (table size)/(number of non-empty buckets)]. Then a tabular printout of the bucket size distribution follows, showing the bucket size, actual number of buckets of that size, and the expected number for simple uniform hashing. The table print terminates for bucket size n when there are no buckets of size > n and the theoretical size is < 0.1.

3. Use the algorithms you developed in Assignment 2.

4. Thoroughly test your implementation for correct functionality using the provided test clients fhtbl.cpp and hasheval.cpp using a variety of tables you create with rantable.cpp. Be sure to test using variations:

   1. Tables of various sizes, small to very large (at least 1,000,000)
   2. Varieties of hash functions (three are provided: KISS, MM, and Simple)
   3. Load factor = n/b = ratio of table size to (approximate) number of buckets (0.1, 1.0, 10.0 100.0 are suggested)
   4. Prime / nonprime number of buckets

   The test harnesses fhtbl.cpp and hasheval.cpp are easily changed via comment/uncomment of typedefs to accomodate the variations in hash functions. The prime/non-prime number of buckets is a constructor argument (default value "true" meaning prime number of buckets).

5. Write a short summary paper giving your experience and lessons learned during the testing of variations as above. Turn this in as a pdf document under Assignment 4.

Hints

• Use Assignment 2 # 3 as a check for internal consistency during Analysis.

• Use Assignment 2 # 7 to calculate the theoretical bucket size distribution.

• Use a vector sizeCount[k] to accumulate number of actual buckets of size k during a single pass through the buckets.