CS 584 - Stream Database Systems
Homework 2: Counting Sample

Assignment
- Implement the the counting sample algorithm discussed in this webpage: click here

Student program

The program must accept the following parameters:

CountingSample Seed N a< inputFile

Meaning of the parameters:

Seed = is the seed for the random number generator used in YOUR program (remember that your program will need to generate random number, well, use this seed) - if you use C, you would call: srandom(Seed)
N = Max size of the counting sample
a = increase in probability (T' = a × T)

Outputs of the program:

The final value of the selection probability (the value (1/T) in the algorithm)
The content of the sample
The output format is a sequence of lines like this:

So the output file looks like this: The format of the data file is:

1/T value1 count1 value2 count2 value3 count3 value4 count4 ...

Note of the class notes

In the webpage classnotes on Counting Sample algorithm, I used:



      // ---------------------------------------------------
      // Reduce counting sample when size exceeds threshold
      // --------------------------------------------------- 
      if ( size(S) > threshold )
      {
	 ...
      }

This will not guarantee to reduce the size. I used the construct to explain the concept.

The correct code is:



      // ---------------------------------------------------
      // Reduce counting sample when size exceeds threshold
      // --------------------------------------------------- 
      while ( size(S) > threshold )
      {
	 ...
      }

Help files
- data1: test input data 1 (50000 values from uniform 1..10000) - click here
- data2: test input data 2 (50000 values from sift distribution 80% [1..1000], 20% [1001..10000]) - click here
  The format of the data file is:
- avg.c: click here
  - Compile with: cc -o avg avg.c
  - Usage: avg < datafile
  - This program computes the average of the INPUT data
- avg2.c: click here
  - Compile with: cc -o avg2 avg2.c
  - Usage: avg2 < outputFile
  - This program computes the adjusted average of the Counting Sample output file
Turn in
- Turn in a Makefile using the command:
```
    /home/cs584001/turnin Makefile hw2
```
  (If you use Java, you still need a Makefile. Let me know if you don't know how to create a Makefile)
- Turn in each program file using this command:
```
    /home/cs584001/turnin Filename hw2-?
```
  where "?" is a number from 0 to 9.

CS 584 - Stream Database Systems Homework 2: Counting Sample

CS 584 - Stream Database Systems
Homework 2: Counting Sample