Data Structures and Algorithm Analysis - Computer Science at ...

Sec. 8.8 Projects 299an external sorting algorithm is used. The company’s payroll program is sogood that it plans to hire out its services to do payroll processing for othercompanies. The president has an offer from a second company with 100times as many employees. She realizes that her computer is not up to thejob of sorting 100 times as many records in an acceptable amount of time.Describe what impact each of the following modifications to the computingsystem is likely to have in terms of reducing the time required to process thelarger payroll database.(a) A factor of two speedup to the CPU.(b) A factor of two speedup to disk I/O time.(c) A factor of two speedup to main memory access time.(d) A factor of two increase to main memory size.8.22 How can the external sorting algorithm described in this chapter be extendedto handle variable-length records?8.8 Projects8.1 For a database application, assume it takes 10 ms to read a block from disk,1 ms to search for a record in a block stored in memory, and that there isroom in memory for a buffer pool of 5 blocks. Requests come in for records,with the request specifying which block contains the record. If a block isaccessed, there is a 10% probability for each of the next ten requests that therequest will be to the same block. What will be the expected performanceimprovement for each of the following modifications to the system?(a) Get a CPU that is twice as fast.(b) Get a disk drive that is twice as fast.(c) Get enough memory to double the buffer pool size.Write a simulation to analyze this problem.8.2 Pictures are typically stored as an array, row by row, on disk. Consider thecase where the picture has 16 colors. Thus, each pixel can be represented using4 bits. If you allow 8 bits per pixel, no processing is required to unpackthe pixels (because a pixel corresponds to a byte, the lowest level of addressingon most machines). If you pack two pixels per byte, space is saved butthe pixels must be unpacked. Which takes more time to read from disk andaccess every pixel of the image: 8 bits per pixel, or 4 bits per pixel with2 pixels per byte? Program both and compare the times.8.3 Implement a disk-based buffer pool class based on the LRU buffer pool replacementstrategy. Disk blocks are numbered consecutively from the beginningof the file with the first block numbered as 0. Assume that blocks are