CPP Performance Optimization & Profiling 2

Question 1

Which cache concept refers to the tendency of programs to access memory locations near recently accessed locations?

Accepted Answer

Spatial locality

Answer

Spatial locality means programs tend to access nearby memory addresses, which is why sequential array traversal is cache-friendly.

Question 2

What is the primary purpose of loop unrolling as an optimization technique?

Accepted Answer

Decrease loop overhead and enable instruction-level parallelism

Answer

Loop unrolling reduces loop control overhead (increment, compare, branch) and exposes more independent instructions for the CPU pipeline.

Question 3

Which C++ standard attribute hints to the compiler that a branch is expected to be taken frequently?

Accepted Answer

[[likely]]

Answer

[[likely]] (C++20) hints that the branch is expected to be taken, allowing the compiler to optimize code layout for that path.

Question 4

What does 'false sharing' mean in the context of multi-threaded performance?

Accepted Answer

Threads access different variables that reside on the same cache line

Answer

False sharing occurs when two threads modify different variables that happen to share a cache line, causing unnecessary cache invalidation traffic.

Question 5

Which profiling technique samples the program counter at regular intervals without modifying source code?

Accepted Answer

Statistical (sampling) profiling

Answer

Statistical profiling periodically samples the PC to estimate where time is spent, with minimal overhead compared to full instrumentation.

(CPP) C++ Programming Professional Certificate Practice Test