CS 280 - Programming Assignment

Information

• Handout
• OAHashTable: HTML Text
• Helper functions:
  • Interface (Support.h) HTML Text
  • Implementation (Support.cpp) HTML Text
• An example driver program: HTML Text
• Some sample output from the driver is provided below. Before attempting to implement this assignment, make sure you understand every line of output. If you don't understand exactly how this output was arrived at, you will have a very difficult time doing the assignment correctly.

• Sample command lines
  • Microsoft: (stress tests: replace /MTd with /MT /O2)

    cl -Fems.exe driver-sample.cpp Support.cpp /EHa /Za /W4 /WX /MTd /D_CRT_SECURE_NO_DEPRECATE
    

  • GNU:

    g++ -o gnu driver-sample.cpp Support.cpp -Wextra -Wall -std=c++14 -pedantic -Wconversion -O2 -g 
    

• Another sample driver: HTML Text   Output

• Double-hashing is almost identical to linear probing. The only difference is the stride. You should have code similar to this in your program:

  unsigned stride = 1; // assume linear probing
  
    // If we are doing double hashing, get the stride/increment
  if (Config_.SecondaryHashFunc_)
    stride = Config_.SecondaryHashFunc_(Key, TableSize_ - 1) + 1;
  

Simple GUI for Viewing

• Download executable

  The GUI shows the hash values of the keys as you move the mouse over them. Makes it easy to see where the keys will be inserted. (The screenshots below do not show this feature.)

  After performing the same steps that are done in the TestDoubleHashing function from the console driver:

  

  The hash functions can be displayed so you can see how they work:

  

Other Data

• The tables below show the efficiency of linear probing and double hashing, using a variety of combinations. The values represent the average number of probes per insertion. The primary hash function is listed on the left and the secondary hash function is listed across the top.

• After adding 75 items to a table of size 101 and a max load factor of 75%:

  	None (LP)	Simple	RS	Universal	PJW
  Simple	31.240	8.560	3.067	2.147	2.533
  RS	7.667	3.507	2.213	3.133	2.147
  Universal	1.493	2.040	2.520	2.427	2.200
  PJW	1.120	1.107	1.440	1.160	1.347

• After adding 95 items to a table of size 101 and a max load factor of 95%:

  	None (LP)	Simple	RS	Universal	PJW
  Simple	40.221	10.579	5.347	2.758	4.053
  RS	11.126	4.442	3.600	5.600	3.295
  Universal	1.853	2.800	3.084	3.526	3.337
  PJW	1.621	1.789	2.432	1.905	2.147