High Performance Computing & AI
Practical notes on Python, JupyterHub, Kubernetes and AI for science — from the San Diego Supercomputer Center.
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GNILC dust templates: impact of the zero-level offset fix
The PySM 3 GNILC dust templates were regenerated after fixing the NumPy indexing bug of issue #281 that left the zero-level offset in the intensity input. This notebook compares the released 2023 templates with the regenerated ones: intensity zero level, polarization fraction, TT/EE/BB spectra, and the mean intensity check of issue #226. A dedicated section answers why the polarization fraction distribution differs from fig. 5 of Planck 2018 XII: the fix places the templates at the low-offset convention of that figure, and the residual is sky region and resolution.
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GNILC dust zero-level offset with the Lenz et al. 2017 low-velocity HI map
The original zero-level measurement used the full HI4PI column density, which includes high-velocity clouds that carry no dust. Redoing it with the Lenz et al. 2017 low-velocity map proposed in the feedback on PySM issue #281 shifts the intercept by only +0.001 MJy/sr: the offset is confirmed at about 0.126 MJy/sr. Includes the residual map requested in the discussion: the low-valued bump is a southern, high-column population that does not track the >90 km/s gas, with hemispheres differing in FIR per unit column but agreeing on the intercept.
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Keeping interactive tutorials up to date with an orchestrator and AI subagents
How to keep browser-based tutorials working with an orchestrator, a browser executor and a documentation improver, instead of hoping nobody follows the outdated step.
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Write slides in Markdown with Marp when working with AI agents
Why keeping presentations in Markdown and building them with Marp works well with AI agents, with a clean reusable theme and an example repository.
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A Marp theme that reproduces the official SDSC slide template
An open source Marp theme that reproduces the official SDSC slide template, extracted from the brand guide PowerPoint file, with a published HTML preview.
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Measuring the zero-level offset of the GNILC dust intensity map with HI4PI
The CIB monopole was never subtracted from the GNILC dust input of the PySM d9/d10/d11 templates because of a NumPy indexing bug; this notebook measures the real zero-level offset of that map from the HI4PI HI correlation.
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Managing projects with GitHub and AI agents: the structure problem
In my previous post about managing projects with GitHub and AI agents I described how I organize events and workshops with a single GitHub repository as the source of truth, issues for every activity, and an agent per collaborator.
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Same 27B model, two worlds: Mac mini vs a data-center GPU
How much does datacenter hardware buy you over an Apple Silicon dev box? To get a feeling for it, I set the NRP managed LLM service, which hosts Qwen3.8-27B (api name qwen3-small) in bf16 on their Nautilus GPU fleet, against my Mac mini (the high-level story is in the experience post, the full setup in the setup post), which serves the same model quantized to NVFP4 on the MLX engine.
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Living with a local 27B LLM on a Mac mini: capable enough and (almost) fast enough
I run an Apple M4 Pro Mac mini in the office as a private LLM server: a 27B Qwen 3.8 model, served over my Tailscale tailnet, used every day by my coding agent to handle emails, Trello cards, and general project work.
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Mac mini as a private LLM server: the technical setup
This is the technical companion to the experience post: how the Mac mini is set up, how every service runs, and where the configuration lives. The benchmark details (prefill, decode, context stress test, agent context sizes) are here too. The data-center comparison is in the comparison post.
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Offline speech-to-text on Linux with nerd-dictation
If you want offline speech-to-text on a Wayland desktop, nerd-dictation is a great choice: it records from your microphone, transcribes locally (no cloud), and types the result into the focused window.
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SLIC superpixels on the HEALPix grid
A recent healpy issue proposes a slic function that generates superpixels on the HEALPix grid, adapting the SLIC algorithm to the sphere, with a complete working implementation attached. This post is what I found testing it.
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PySM: produce CAR output at the smoothing stage
PySM 3 only builds HEALPix skies. Here is how to produce CAR pixelization output at the smoothing stage with a single spherical harmonic transform, and a validation against the smooth-then-reproject route.
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healpy 1.20.1: last release with macOS 14 wheels
The healpy 1.20.1 release includes bug fixes and is the final release to provide macOS 14 arm64 wheels before the GitHub runner retirement.
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A practical primer on software citation
Software forms the foundation of modern research, yet citing code effectively remains a challenge across scientific disciplines.