# \#mapreduce

**URL:** https://discourse.julialang.org/tag/mapreduce/1677.md

[Latest](https://discourse.julialang.org/latest.md) · [Categories](https://discourse.julialang.org/categories.md) · [Tags](https://discourse.julialang.org/tags.md)

---

## [Argmax mapreduce on GPU](https://discourse.julialang.org/t/argmax-mapreduce-on-gpu/134971)

<div class="topic-metadata">

**Author:** [@noetheriankoala](https://discourse.julialang.org/u/noetheriankoala)\
**Replies:** 6\
**Last updated:** [April 21, 2026, 9:35am UTC](https://discourse.julialang.org/t/argmax-mapreduce-on-gpu/134971 "2026-04-21T09:35:03Z")

</div>

Hello! I am trying to quickly compute \\text{argmax}\_{\\substack{1 \\leq s \\leq k\\\\ k+1 \\leq t \\leq n}} A\_{s,t} + (1-\\ell\_s)(1 + \\ell\_t) I do this on the CPU with the following code. f = ((i, j),) -\> (i, j, A\[i, j\]^2 + …

---

## [Improving Base.mapreduce by 20% on vectors](https://discourse.julialang.org/t/improving-base-mapreduce-by-20-on-vectors/134478)

<div class="topic-metadata">

**Author:** [@epilliat](https://discourse.julialang.org/u/epilliat)\
**Replies:** 2\
**Last updated:** [December 12, 2025, 1:32pm UTC](https://discourse.julialang.org/t/improving-base-mapreduce-by-20-on-vectors/134478 "2025-12-12T13:32:17Z")

</div>

Hello everyone, I’ve been exploring reduction operations on GPUs recently, and this led me to investigate CPU performance as well. I discovered that we can improve mapreduce in Base while maintaining full precision for …

---

## [Type-instability of mapreduce vs. map + reduce](https://discourse.julialang.org/t/type-instability-of-mapreduce-vs-map-reduce/121136)

<div class="topic-metadata">

**Author:** [@gdalle](https://discourse.julialang.org/u/gdalle)\
**Replies:** 18\
**Last updated:** [October 10, 2024, 4:43pm UTC](https://discourse.julialang.org/t/type-instability-of-mapreduce-vs-map-reduce/121136 "2024-10-10T16:43:03Z")

</div>

I’m a bit surprised that in this simple example, f is type-stable but g is not. Is this a JET.jl issue (@aviatesk) or a Julia issue? using JET function f(m, n) blocks = map(1:n) do i ones(m) end ret…