Another pitfall cited in Section 1.10 is expecting to improve the overall performance of a computer by improving only one aspect of the computer. Consider a computer running a program that requires 250 s, with 70 s spent executing FP instructions, 85 s executed L/S instructions, and 40 s spent executing branch instructions. 1.13.1 [5] <§1.10> By how much is the total time reduced if the time for FP operations is reduced by 20%? 1.13.2 [5] <§1.10> By how much is the time for INT operations reduced if the total time is reduced by 20%? 1.13.3 [5] <§1.10> Can the total time can be reduced by 20% by reducing only the time for branch instructions?

1) 236 s

2) 91%

3) no

Explanation:

solution:

The new time required to run FP operations is

0.8 x 70 s = 56 s

So, the new time required to run the program is

250 — (70 — 56) = 236 s (because we reduced the time of execution by 70 — 56 = 14 seconds).  

The new total time of execution is  

0.8 x 250 = 200 s  

If we assume that we changed only the time needed to execute INT operations, the new time needed to execute INT operations is

200 — 70 — 85 — 40 = 5 s

Since the old time was 250 — 70 — 85 — 40 = 55 seconds, and  

5/55=0.09

this is the decrease of a whooping 91%!

Let's assume that we completely avoid using branch operations. Then the time of execution is  

55 + 70 + 85 = 205

This is the decrease of 18%, since 205/250 = 0.82 This means that we cannot decrease the total time by 20% by just decreasing the time of branch operations.

the warning light flashes for a second or two when the engine starts. if it stays on, there's must be something wrong with the coolant. you should never dare to continue driving when the light is on. pull over as soon as possible and shut the engine off.

hope this is what you're talking about