Páll Melsted's Avatar

Páll Melsted

@pmelsted

Professor @hi.is in CS, head of rna seq data analysis at decode genetics (views are mine). Bioinformatician, epistemic trespasser, &c. ps. I hate GTF files

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29.09.2023
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Latest posts by Páll Melsted @pmelsted

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a man stands in front of a sign that says microsoft web developers ALT: a man stands in front of a sign that says microsoft web developers
07.03.2026 14:10 👍 1 🔁 0 💬 0 📌 0

Cuda. I tried a long time ago to build something with opencl and found out that there is no support. AMD has had plenty of time to work with developers since then but nothing has happened.

I guess NVIDIA figured out that Ballmer was right, it’s all about the developers

06.03.2026 21:49 👍 3 🔁 0 💬 3 📌 0

Coming next week

06.03.2026 21:24 👍 2 🔁 0 💬 0 📌 0
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ok, that figure looked fine in the preview but was transparent, here's a better version

06.03.2026 19:38 👍 10 🔁 0 💬 0 📌 0

The only downside to this work is that now I feel frustrated having to wait minutes for classical kallisto to finish

06.03.2026 19:32 👍 5 🔁 0 💬 1 📌 0

like dealing with sparse arrays, variable sized lists and things we would solve with dynamic memory allocation on the CPU.

06.03.2026 19:32 👍 3 🔁 0 💬 1 📌 0

and over again. Prefix scan. If you are interested in learning more about this then read this paper www.cs.cmu.edu/~guyb/papers... by Guy Blelloch from 1990. It is one of the most clearly written papers I've read and it gives you the algorithmic building blocks to solve problems on GPUs

06.03.2026 19:32 👍 9 🔁 0 💬 1 📌 0

Contrary to regular scientific programming, where the state consist of a high dimensional vector and most operations are matrix multiplication, string processing does not have obvious programming paradigms that port easily to GPUs. And yet in this work we always wind up using the same tool over ...

06.03.2026 19:32 👍 6 🔁 1 💬 1 📌 0

The key insight (aside from the speed) is that we need to reconsider all of the algorithmic framework if we want to use GPUs for large scale processing of sequencing datasets. It's nontrivial but I hope this paper gives some insight into how it's possible.

06.03.2026 19:32 👍 6 🔁 0 💬 1 📌 0

For a large dataset (295M reads) the GPU version took 50 seconds. Just running zcat on the files takes 10 minutes! Decompression and parsing FASTQ is a major bottleneck . Instead of using kseq we moved this work parsing to the GPU which delivers amazing throughput.

06.03.2026 19:32 👍 2 🔁 0 💬 1 📌 0

Figure 1 shows the main results, we can run 30M paired end reads in under 10 seconds using a RTX 5090 NVIDIA GPU. The average speedup is 30x for smaller reads and that includes startup time, on average we can process about 3.6M paired end reads per second.

06.03.2026 19:32 👍 5 🔁 0 💬 1 📌 0
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Excited to share this preprint that describes my latest work on using GPUs to accelerate processing of RNA-seq data.

The title says it all: "RNA-seq analysis in seconds using GPUs" now on biorxiv www.biorxiv.org/content/10.6... and github github.com/pachterlab/k...

Figure 1 shows they key result

06.03.2026 19:32 👍 126 🔁 55 💬 5 📌 7

2015: growing almonds consumes too much energy and water
2026: growing kids consumes too much energy and eater

bsky.app/profile/x2y....

22.02.2026 16:18 👍 3 🔁 0 💬 0 📌 0

Jafngóð og bókin?

18.02.2026 21:14 👍 0 🔁 0 💬 1 📌 0
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In pretty sure I’m thoroughly radiated after this

10.01.2026 21:50 👍 6 🔁 0 💬 0 📌 0

I’ve been exploring different models in cursor and opus 4.5 is amazing. I often ask it to sketch out code with the prompt “do not make any modifications to the code” and ask about my assumptions and poke holes, only when I agree can it proceed

28.12.2025 10:59 👍 1 🔁 0 💬 1 📌 0
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Spotify wrap up is so last year

23.12.2025 10:37 👍 2 🔁 0 💬 0 📌 0

I also learned today that Nirvana is not “niche”. But then again this is the generation that invented 6-7

08.12.2025 17:29 👍 0 🔁 0 💬 0 📌 0

14yo: I need a niche music recommendation
Me: how about Godspeed You! Black Emperor, let’s find it

*not found on Spotify*

Me: That’s how nice they are

08.12.2025 17:17 👍 2 🔁 0 💬 1 📌 0

Today I found out that the Pacbio tools for working with barcodes and adapters in Kinnex are called lima and skera. To whomever came up with that joke, I salute you, you’ve reached 50% of the audience

31.10.2025 14:06 👍 0 🔁 0 💬 0 📌 0

Retracting a paper is going to hurt

21.10.2025 20:01 👍 2 🔁 0 💬 0 📌 0

All right, I posed this question to my PhD student this morning and he looked at me funny and asked if it was a trick question

What is the running time of this code

a, b = 0, 1
for _ in range(2, n+1):
a, b = b, a + b
return b

07.10.2025 22:12 👍 1 🔁 0 💬 0 📌 0

Happy Q4 for those who celebrate

01.10.2025 20:31 👍 1 🔁 0 💬 0 📌 0

Today I fixed a humming converter and an intercom receiver set from the 70’s. I’m surprised at how good ChatGPT is at diagnosing problems and coming up with fixes for hardware that is older than me. Since I didn’t have to replace the units I can justify the cost and environmental impact of AI

27.09.2025 23:28 👍 3 🔁 0 💬 0 📌 0

The Genome Informatics conference (@ Cold Spring Harbor Lab, Nov 5 - 8) abstract deadline is **today**. We welcome your submissions! Topics include:
- PanGenomes
- Genome Assembly & Seq. Algos.
- Algorithmic Evo. Bio
- Single Cell & Spatial Omics
- Microbial Genomics
- AI/ML & Integrative Omics
🙏🙏🙏

22.08.2025 15:00 👍 11 🔁 6 💬 0 📌 0
Preview
a group of men in suits are dancing around a coffin . ALT: a group of men in suits are dancing around a coffin .
15.08.2025 05:14 👍 2 🔁 0 💬 0 📌 0
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Perfect marketing doesn’t exi…

05.07.2025 11:22 👍 1 🔁 0 💬 0 📌 0

Glengarry Glen Ross

05.07.2025 10:41 👍 1 🔁 0 💬 0 📌 0
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It is by the juice of coffee that thoughts acquire speed …

27.06.2025 12:39 👍 2 🔁 0 💬 0 📌 0
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Postdoctoral Researcher in Computational Genetics The research group of Oliver Stegle looks for a postdoctoral researcher to join a collaborative project with GSK with the goal to apply computational methods to investigate the effects of rare variant...

Job alert: Join us for a postdoc in AI in genetics at @EMBL Heidelberg! Great collaboration with @Adrian Cortes @GSK, aiming to develop new tools to elucidate genetic effects using population-scale cohorts and single-cell readouts. Please share!

embl.wd103.myworkdayjobs.com/de-DE/EMBL/d...

26.06.2025 10:00 👍 15 🔁 18 💬 0 📌 2