CS Performance Optimization 5

Question 1

A service is CPU-bound at 100% on one core while other cores sit idle. Which change most directly improves throughput?

Accepted Answer

Parallelizing the workload across multiple cores

Answer

A single-threaded CPU-bound workload benefits from splitting work across the idle cores.

Question 2

What is the purpose of SIMD (Single Instruction, Multiple Data) instructions in performance optimization?

Accepted Answer

Applying one operation to multiple data elements simultaneously

Answer

SIMD vectorizes computation, processing several values per instruction.

Question 3

Which strategy improves performance for a read-heavy web API whose data changes infrequently?

Accepted Answer

Caching responses with an appropriate expiration policy

Answer

Caching serves repeated reads without recomputation, ideal when data rarely changes.

Question 4

A string is built by concatenating inside a loop in a language with immutable strings, resulting in O(n²) behavior. What is the standard fix?

Accepted Answer

Use a string builder or buffer and join once at the end

Answer

A mutable buffer avoids copying the entire accumulated string on every append.

Question 5

What does 'lazy evaluation' contribute to performance?

Accepted Answer

Avoiding computation of values that are never actually used

Answer

Deferring evaluation until a value is needed skips work for unused results.

(CS) Computer Science Practice Test