Intermediate Topic 34 of 51 Concurrency & Parallelism
Parallel Prefix Sum
Scan primitive computing running totals in parallel.
How it works
The scan computes running totals in O(log n) steps (Hillis-Steele or Blelloch up-sweep and down-sweep), a building block for sorting, stream compaction and allocation.
Where it is used
GPU algorithms.
Common pitfall
Work-efficient versions need more careful indexing.
Where it fits in the course
Parallel Prefix Sum is topic 34 of 51 in Concurrency & Parallelism, rated Intermediate. It follows Parallel Reduction. The next topic is OpenMP.
Practice and explore
- Open the interactive lesson, with a mini quiz.
- Take the Concurrency & Parallelism quiz.
How to study this topic
- Read the explanation above and restate the definition in your own words.
- Open the interactive lesson and answer its mini quiz.
- Read the common pitfall, then write a short example that avoids it.
- Check your understanding in the Concurrency & Parallelism quiz, and revisit the topic if you miss a question.
Frequently asked questions
What is Parallel Prefix Sum?
Scan primitive computing running totals in parallel. It belongs to Concurrency & Parallelism and is an intermediate-level topic.
Where do people use Parallel Prefix Sum?
GPU algorithms.
What is the most common mistake with Parallel Prefix Sum?
Work-efficient versions need more careful indexing.
What should I learn before this topic?
Start with Parallel Reduction, the topic just before it in Concurrency & Parallelism.
How can I practice it?
Answer the mini quiz in the interactive lesson, then take the Concurrency & Parallelism quiz.
Is Parallel Prefix Sum hard to learn?
It is an Intermediate topic. Be comfortable with the Beginner topics in this area first, then read the common pitfall carefully, since it is where most mistakes happen.
How long does it take to learn Parallel Prefix Sum?
Most learners can read the explanation and finish the interactive lesson in under an hour. Fluency comes from applying the idea, so plan a few short practice sessions with the quiz.
Which topics are related to Parallel Prefix Sum?
Parallel Reduction, OpenMP, Fork-Join Model are closely connected. The full list is in the related topics section of this page.
What should I study after Parallel Prefix Sum?
Continue with OpenMP, the next topic in Concurrency & Parallelism.
Related topics
- Parallel Reduction (Concurrency & Parallelism)
- OpenMP (Concurrency & Parallelism)
- Fork-Join Model (Concurrency & Parallelism)
- MPI (Concurrency & Parallelism)