COMP 235, Fall 2022, Homework 2

Amdahl’s Law and Data Representation

Due by September 30 by the start of class.

1. You have written a new program in assembly language, using only 4 types of instructions. Let’s call them types A, B, C, and D. Your program consists of 20% type A instructions, 40% type B, 30% type C, and 10% type D. You timed the program and it takes 100 seconds on your laptop.

   A. Your friend suggests replacing all the type D instructions with another type, E, which is 10x faster. How long will the improved program take to run?

   B. Consider the original program (no type E instructions). You are considering buying a new laptop which happens to execute type B instructions faster. How much faster (by what factor) must it execute type B instructions to get a total running time of 80 seconds? Assume that the new laptop executes types A, C, and D the same as your old laptop.

2. 2.58 (from CSAPP)
3. 2.59
4. 2.61
5. 2.71. For part B, you need not limit yourself to left and right shifts and one subtraction; you may solve it anyway you’d like.
6. 2.72.