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casta | 5 months ago

How's the prefix sum on a single thread O(N log(N))? Isn't it trivially O(N)? It's just a for loop.

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TimorousBestie|5 months ago

Yes, but for loop comes with all those data dependencies that prevent it from being parallelized trivially.

The algorithm with fewer data dependencies is O(N log N).

This is covered in more detail in the article.

gyrovagueGeist|5 months ago

It's from the depth of the computation, not the work