# Prefix Sums (Scan)

*Module of the free GPU.js GPGPU course · 6 tasks*

Running totals in parallel — the doubling ladder, exclusive scans, and the offsets every variable-sized output depends on.

## Tasks

1. [The Sum So Far](https://gpu.rocks/learn/prefix-sum-351cfa41/1.md)
2. [Everyone Sums Their Own Prefix](https://gpu.rocks/learn/prefix-sum-351cfa41/2.md)
3. [The Doubling Ladder](https://gpu.rocks/learn/prefix-sum-351cfa41/3.md)
4. [Inclusive, Exclusive, and Why It Matters](https://gpu.rocks/learn/prefix-sum-351cfa41/4.md)
5. [Work-Efficient: Upsweep, Downsweep](https://gpu.rocks/learn/prefix-sum-351cfa41/5.md)
6. [Payoff: Offsets Place the Data](https://gpu.rocks/learn/prefix-sum-351cfa41/6.md)

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Interactive version: https://gpu.rocks/learn/prefix-sum-351cfa41