Pablo Fernandez

Open Source Projects & Contributions

Last updated: 2026-10-11

These are my contributions to open source projects.

Machine Learning

PyTorch: Keep nested learning-rate schedulers from skipping a step

SequentialLR advanced a nested SequentialLR or ChainedScheduler during construction. The extra step made wrapped schedulers reach milestones or apply decay one epoch early, and emitted a misleading step-order warning before user code had called step(). The fix gives composite schedulers an initialization path that prepares their state without advancing their children, with regression tests for both scheduler types.

PyTorch: Make ReduceLROnPlateau composable

ReduceLROnPlateau cannot be used inside SequentialLR or ChainedScheduler, a limitation with issues open since 2021. This change adds optional metric forwarding, aligns the scheduler with the normal composition lifecycle, preserves initial_lr, supports milestone handoffs, and reports a clear error when the required metric is missing. It is the smaller of two alternative designs I submitted for the same problem, so the maintainers can pick one.

PyTorch: Introduce a composable PlateauLR

The more extensive of the two designs. It introduces PlateauLR, an LRScheduler-based replacement for ReduceLROnPlateau that composes with other schedulers. The change forwards metrics through nested schedulers, covers milestone handoffs and compatibility with third-party schedulers, and updates the documentation.

PyTorch: Fix stale errno handling in MapAllocator

Multi-worker data loading could fail with a misleading shared-memory error. I traced it into ATen’s MapAllocator, a C++ component, where the code read the stale process-global errno instead of the error value that posix_fallocate returns directly, and supplied the exact fix in the issue. Another contributor landed that fix unchanged, so the diagnosis and the fix are mine and the commit is theirs.

PyTorch Lightning: Prefix Trainer-generated metric keys

Added log_key_prefix to Trainer for the metrics Lightning generates itself. Trainer(log_key_prefix="trainer/") logs the automatic epoch key as trainer/epoch, without renaming metrics logged by application code. This is the first of three parts of a larger proposal, which I also submitted as a single combined PR so the maintainers could review it either way.

PyTorch Lightning: Avoid negative epoch totals for unlimited training

RichProgressBar displayed impossible totals such as Epoch 5/-2 when max_epochs=-1 meant unlimited training. The fix omits the total in that case and includes a regression test.

PyTorch Lightning: Mark failed W&B runs as failed

WandbLogger.finalize("failed") returned without finalizing the W&B run. If the process then exited with code 0, W&B’s exit handler marked a crashed training run as successful, which corrupts sweep results. The fix explicitly finishes the experiment with a failing exit code.

PyTorch Lightning: Control the W&B global_step prefix

The second part of the metric-key proposal. It adds log_key_prefix to WandbLogger for its generated step-axis key, makes bare global_step the default, and lets users restore or choose a namespace such as trainer/global_step, independently of the existing prefix for pass-through metrics.

PyTorch Lightning: Make Comet’s epoch key configurable

The third part of the metric-key proposal. It adds epoch_key to CometLogger, replacing its hardcoded extraction of epoch. This supports prefixed keys such as trainer/epoch and allows epoch extraction to be disabled, while preserving the existing behavior by default.

torchmil: Keep CAMIL predictions independent of padding

CAMIL gave a different prediction for the same bag depending on what it was batched with. The mask was not passed to the Nyström transformer layer, and the local self-attention normalized its weights with a softmax over every position, so padded instances took a share of the attention. The fix passes the mask through and uses masked_softmax, so each bag in a padded batch gets the prediction it gets alone.

torchmil: Support variable-size bags in TransMIL

TransMIL silently dropped the mask produced by collate_fn and treated padded instances as real ones. With this change, sequence squaring happens per bag, empty grid cells are zeroed before the positional encoding, and NystromAttention processes a masked sequence as if its masked positions were not there. Every bag in a batch computes its single-bag result while the batch is still processed in one pass.

torchmil: Keep DTFDMIL predictions independent of padding

DTFDMIL gave a different prediction for the same bag depending on how much masked padding it carried. The second tier pooled the distilled features without a mask, so zero-padded instances took a share of its attention. The fix carries a mask alongside the distilled features, and also stops the maxmin and max distillation modes from crashing when the optional mask is omitted.

torchmil: Fix SmoothTop1SVM target broadcasting

CLAM’s default instance loss silently combined predictions from different instances instead of measuring each instance independently. Repeating identical predictions and labels changed the reported mean loss, and training used gradients from the wrong objective. The fix corrects the losses and gradients for CLAM’s column labels and restores support for the documented vector labels.

torchmil: Exclude padding from ProbSmoothAttentionPool regularization

ProbSmoothAttentionPool applied the instance mask during pooling but ignored it when computing the regularizer, so masked padding changed the regularization loss for an otherwise identical bag. The fix excludes padded means and covariance terms and normalizes by each bag’s real instance count, which corrects ProbSmoothABMIL, SmoothABMIL, and TransformerProbSmoothABMIL.

torchmil: Disable MultiheadSelfAttention dropout in eval mode

MultiheadSelfAttention applied attention dropout in eval mode, so repeated calls with identical inputs and weights produced different outputs. The fix passes a zero dropout probability to scaled_dot_product_attention during evaluation and keeps the configured probability during training.

Rust

Zed: Fix remote connections from locally built Zed

Locally built Zed binaries failed to connect to Dev Containers, SSH hosts, or WSL. I traced the crash to the remote server’s debug-embed Cargo feature not reaching the utility crate that embeds Zed’s default settings, then fixed the feature wiring.

Zed: Preserve Docker exec command arguments

A regression in Zed’s Dev Container support flattened lifecycle commands into one string before passing them to Docker. That lost argument boundaries, so a command such as npm update could silently run only npm. The fix keeps each argument distinct and brings postStartCommand marker handling in line with the upstream Dev Container CLI.

Python

Django: Remove wildcard imports

Submitted six patches replacing wildcard URL imports across Django’s project template, core, contrib apps, documentation, and tests. The final 88-file commit completed the cleanup, moved the URL functions and handlers into django.conf.urls, deprecated django.conf.urls.defaults, and thanked me and Craig de Stigter for the patches. I am listed in Django’s AUTHORS file.

Python: Port test skipping to Python 3’s unittest

Ported an older test-skipping proposal from Python 2.3.3 to the then-current Python 3, integrated its tests into Python’s test suite, and updated the doctests affected by the new TestCase output. A core reviewer said the patch looked good. Test skipping shipped in Python 2.7 and 3.1 in a broader implementation by Benjamin Peterson, with decorators, class-level skipping, and expected failures.

Python: Prototype nonfatal expectations for unittest

Adapted a testing feature for Python’s standard unittest library. The patch added expect* counterparts to seven assertion methods, so a test collects multiple failures instead of stopping at the first one, together with tests for passing, failing, and error cases.

SCons Erlang

An extension that teaches the SCons build system how to compile, document, install, and package Erlang projects. It supplies an erlang.py SCons tool plus an Erlang dependency scanner, and builds Serlvers and Fanterlastic Four, listed under Erlang below.

SCons Chicken

An extension that teaches the SCons build system how to build projects for Chicken, the Scheme-to-C compiler. It supplies builders and worked examples for programs and libraries, detects the local Chicken repository, and generates the .setup metadata used to install extensions. Later work made builds incremental, added a scanner so included Scheme sources trigger the right rebuilds, and introduced a ChickenEgg builder for packaging.

Ruby and Rails

Repeater World

A directory of amateur radio repeaters, built as a Rails application, with both the service and its data free to use. It imports and reconciles data from national and regional sources across the UK, Ireland, Finland, Australia, and the United States, with scheduled importers, data-cleaning rules, and geocoding around inconsistent real-world records. It supports geographic, grid-square, country, distance, and free-text searches across analog and digital modes, and exports programming files for Icom, Yaesu, and Baofeng radios and for CHIRP, alongside CSV and JSON.

validation_auditor

A Rails gem that records failed model validations for later analysis, so a rule that blocks legitimate users becomes visible without waiting for someone to report it. A model opt-in stores the messages, and an optional controller hook adds parameters, URL, and user agent, respecting Rails’ sensitive-parameter filters and handling uploads.

random_unique_id

A Rails gem that gives Active Record objects short, non-sequential public identifiers while keeping their database IDs internal, which hides record counts and stops users from predicting adjacent URLs. It overrides to_param, adds relationship helpers and migration support for existing records, retries collisions with progressively longer IDs, and offers UUID generation for large tables.

action_texter

A provider-neutral SMS interface for Ruby applications. Application code builds and delivers a message without knowing which client sends it, so production can use Nexmo or Twilio while tests use an in-memory backend. It includes interceptors that can modify or cancel outgoing messages, observers for delivery results, and phone-number normalization.

assert_difference

A rework of Rails’ assert_difference into a compact assertion for checking several effects of one operation. A hash expresses, in one block, that one record count rose, another fell, and a third stayed within a range, and failures report every counter that missed its expectation. It supports Test::Unit, Active Support, and RSpec.

Rails: Fix dropping indexes on tables with reserved names

Active Record failed to remove an index when the table had a reserved SQL name such as values. The patch made remove_index! quote the table name and added a regression test that creates a values table, adds an index, and removes it without raising. A follow-up tightened the test so the assertion covered both adding and removing the index.

ubiquitous_user

A Rails gem that removes mandatory registration as the price of interacting with a site. It creates a minimal anonymous user on demand, stores that identity in the session, and lets the application attach the activity to a real account later, when the person chooses to sign in.

rails_openid

A small Rails wrapper around ruby-openid that removes the repetitive integration work from applications. It supports Rails 2.3 and 3 and includes an open_id_scaffold generator that creates the association model, controller flow, and tests.

image_button_to

Rails could build form-backed text buttons and standalone image submit tags, but not form-backed image buttons. This gem supplies image_button_to, image_button_to_remote, and image_button_to_function. I also proposed the capability to Rails, where the maintainers liked the use case.

C and C++

Asterisk: Add real-time agent support

Implemented database-backed agents for chan_agent in C, analogous to Asterisk’s real-time SIP and dialplan configuration. The work introduced a find_agent() abstraction, made agent login retrieve records from the real-time backend, and included documentation and code cleanup. Other contributors kept the patch up to date after my initial work, and one reported using it heavily in production.

Score Reading Trainer

A desktop application for practicing reading sheet music, written in C++ with Qt and KDE. It generates configurable random notation and advances only when the player enters the matching note through a computer keyboard or MIDI. It reached four releases, gained German and Spanish translations, and was packaged in Debian from Etch through Squeeze.

File Activity Viewer

A graphical equivalent of tail -f for watching text and log files grow, written in C++ with Qt and KDE for Linux and BSD. It supports several files in one window and is available in English and Spanish.

KTTSD: Build the initial KDE text-to-speech service

Started KTTSD by refactoring Proklam into a KDE text-to-speech service, then separated the service from its speech engines through plugins. The initial tree included command, Festival, Festival client/server, and FreeTTS backends, a client library, configuration interfaces, and the standalone service. KDE contributors developed it much further and renamed it Jovie.

KDE Workspace: Build the accessibility control module

Built the replacement KDE accessibility control module in 19 commits. The work moved the interface to Qt Designer, converted the module to KGenericFactory, wired its Apply actions, loaded and saved audible-bell configuration, added contextual help, and prepared the accessibility daemon to move into kded.

KatePart: Improve syntax highlighting

Reworked KatePart’s PHP syntax definition so it covered the full set of language constructs and recognized them inside strings, then improved the parser documentation and robustness notes. Also fixed KatePart looking for syntax definitions under kate/ instead of katepart/. 14 commits in total.

Kopete: Improve contact dialogs

A series of layout and widget improvements across Kopete’s away, now-listening, and add-contact dialogs for the Gadu-Gadu, IRC, Jabber, and MSN protocols. The 13 commits repaired clipped layouts, made forms resize dynamically, replaced generic Qt widgets with their KDE equivalents, and cleaned up the surrounding C++.

KMag: Keep the magnifier aligned with the mouse at screen edges

KMag failed to refit its selection rectangle after the zoom level changed, which prevented the magnified view from following the mouse all the way to the screen edges.

KMag: Remove the selection rectangle on exit

KMag left its selection rectangle on screen after the application closed. The fix hides the rectangle during destruction.

Smaller fixes

  • KMag: Removed compiler warnings by dropping an unused event parameter and making floating-point-to-integer conversions explicit. Commit dd0c129 · Merged 2003-03-05
  • KMouseTool: Removed compiler warnings by dropping an unused timer-event parameter and making numeric conversions explicit in the sizing calculations. Commit 23103d5 · Merged 2003-03-05
  • KGpg: Rebuilt the second page of the options dialog around dynamic layouts so its controls resize and align correctly. Commit 9ccfc26 · Merged 2002-12-03

Clojure and ClojureScript

Reagent Toolbox

A Reagent-friendly wrapper around the React Toolbox component library. It converts Reagent elements nested inside property maps into React elements, normalizes values and change handlers, and adapts child content to Reagent’s data-oriented component style, across most of the component library.

Free-form

A form library for Reagent applications, with an optional re-frame integration, that leaves both data flow and HTML markup under application control. Special attributes connect ordinary Reagent elements to values and errors, and an extension system generates repeated structures such as Bootstrap 3 forms. It covers nested values, validation messages, selects, text areas, checkboxes, radio buttons, and controlled inputs.

ClojureScript: Route Node.js headers consistently

Optimized and unoptimized Node.js builds emitted headers through different paths in the ClojureScript compiler. The patch routed both through the same add-header helper and was merged by David Nolen.

Prerenderer

Server-side rendering for ClojureScript single-page applications, so crawlers and link-preview services receive real content. An initial Nashorn implementation reached 17.1 seconds per request under load, so I moved execution to a pool-managed Node.js process, which brought the JavaScript execution path down to roughly 46 milliseconds. The library hides the process management and HTTP bridge behind a Clojure API, supports relative AJAX requests, and includes a re-frame integration that considers a page ready once its event queue goes quiet.

jar-copier

A Leiningen plugin that copies selected dependency JARs into an application’s resources as part of the build. It exists for cases such as Java agents, which must be present as a separate JAR at JVM startup, where committing a binary copy would bypass dependency management.

to-jdbc-uri

A small library that converts environment-provided database URLs into the JDBC URLs that Clojure database libraries expect. It started with Heroku PostgreSQL, then added MySQL, Red Hat OpenShift, URL parameters, and pass-through handling for URLs already in JDBC form.

conman

A database connection library for the Luminus and YeSQL stack, combining pooled connections, dynamically rebound transaction connections, and macros that turn SQL files into connection-aware functions. It began as a collaboration with Dmitri Sotnikov of Luminus, who wrote the initial public commits. The Luminus project maintains it and has developed it much further.

Erlang

Serlvers

A set of Erlang behaviours and infrastructure for implementing TCP/IP and UDP services without repeating protocol plumbing. Echo, Chargen, Daytime, and Time serve as deliberately simple reference implementations. Later development moved flow control into the shared launcher and began a DNS implementation.

Fanterlastic Four

The worked example for Serlvers: a supervised Erlang/OTP application running four of the Internet’s simplest standardized services, Echo, Chargen, Daytime, and Time. It exercises the full toolchain around the library, with OTP application and release files, generated EDoc documentation, and builds through SCons Erlang.

Other

xkeyboard-config: Add Esperanto overlays

Added QWERTY and Dvorak overlays that place Esperanto’s six supersigned letters on the third keyboard level. The current symbols/epo source still names me as the contact for the overlays.

Zed: Diagnose ignored Dev Container feature installation order

Zed ignores installsAfter metadata for Dev Container features. Without the dependency graph the Features specification requires, it sorts every feature in a single round and can install a dependent feature first, breaking otherwise valid container builds. The report includes a minimal reproduction and a comparison with the reference Dev Container CLI.

Documentation and project maintenance

  • torchmil: Corrected the documentation build command in the pull request checklist so it matches how the project builds its documentation. PR #34 · Opened 2026-10-09
  • PyTorch Lightning: Turned every actionable item in the pull request template into a checkbox. PR #21789 · Opened 2026-06-28
  • KUser: Added API documentation for the error queue, global user and group state, and application initialization, with notes identifying unsafe or unclear global-state behavior. Commit 6015bd7 · Merged 2004-04-17
  • KMouth: Corrected the documentation’s DocBook declaration from a variant that did not build to one that did. Commit 24ba441 · Merged 2003-01-25