Practice question · Multiple choice
A program is made to run on eight cores instead of one and gets four times faster, not eight. What sets the ceiling?
Hints
- Suppose a fifth of the work must run in order. What happens to that fifth as cores are added?
- Take the number of cores to infinity. What is left?
Show the answer
B. The sequential fraction, which bounds the speedup however many cores you add
Why
The sequential part does not shrink, so it becomes the whole runtime as cores multiply: 20% sequential caps you at five times with infinite hardware. It is why parallelising is a design problem rather than a procurement one, and why the interesting question is always which fraction is genuinely serial.
Practise Machine-Level Debugging Logic
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