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THE FEUTEX TOOLKIT

External Merge Sort IO Plan

Estimate initial sorted runs, merge passes and full-dataset disk traffic.

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FormulaInitial sorted runs = Math.ceil(size/memory); Merge passes = Math.ceil(Math.log(Math.ceil(size/memory))/Math.log(fan)); Total read and write traffic = 2*size*(1+Math.ceil(Math.log(Math.ceil(size/memory))/Math.log(fan)))

Made for real tasks

  • Estimate initial sorted runs, merge passes and full-dataset disk traffic.
Explore step-by-step workflows →

Worked example

Inputs

Dataset size
1000 GB
In-memory run capacity
10 GB
Merge fan-in
8 runs

Expected results

Initial sorted runs
100 runs
Merge passes
3 passes
Total read and write traffic
8000 GB

Load the example in the workspace to reproduce these results. Display rounding does not change the underlying calculation.

How to use this tool

  1. Enter dataset size, in-memory run capacity, merge fan-in in the displayed units.
  2. Calculate the scenario, then compare it with measurements before changing a system.

Try this example

{
  "size": 1000,
  "memory": 10,
  "fan": 8
}

Accuracy and scope

Full initial read/write and full read/write for every merge pass; ignores partial final fan-in and compression.

Is my data uploaded?

This tool runs locally in your browser. Input and output are not sent to a processing server. Copy or download your result before leaving the page.