Scientific Computing

Switching to CMake from autotools or plain Makefiles gives generally better support of many operating systems, in particular Windows. Another benefit is generally faster speed of configuration and build. In 2020, MonetDB switched from autotools to CMake. They observed MonetDB with CMake builds in 40% of the original time. Note also the improvement due to Ninja instead of GNU Make.

We have converted a number of projects from autotools to CMake. Consider automated autotools to CMake script and then manually compare or redo by inspection of the autotools scripts.

In general, livestream data bandwidth depends on the video content (lots of motion vs. talking head) and wireless conditions.

YouTube Live has a wide range of livestreaming modes. Consider 480p to start to keep the connection from dropping out, with data bandwidth of 500 - 2,000 kbps ~ 16 Mbyte/minute. Use variable bitrate to dramatically reduce upload bandwith needed for typical livestreaming scenes. OBS Studio is among streaming software supporting HLS for ease and robustness or low latency RTMPS.

Hugo shortcodes are a powerful, easy way to template code used in blogs and websites. Ana Ulin describes a one-line Hugo shortcode to inline HTML in Hugo:

Under the top-level Hugo website Git directory, add file “layouts/shortcodes/rawhtml.html” containing:

{{.Inner}}

Then in the Markdown file for the particular blog post, do like (removing the space between the left brace and the left caret):

{{ < rawhtml >}}
<p>arbitrary HTML here</p>
{{ < /rawhtml >}}

example

Compare files between Git branches with a GUI like VS Code or Meld, showing all files different between the current Git branch to another Git branch “develop”:

git difftool develop

Compare a single file to another Git branch “develop”:

git difftool develop -- src/myfile.c

For projects consisting of more than a few files, or of files in different code languages, it can sometimes be beneficial to only run certain workflows depending on which files changed. For example, consider a Fortran-based simulation where the CI takes minutes or hours to run, with associated Python plotting code. If only the plotting code is changed, it might not be necessary to CI the entire simulation, but instead test just the Python code. This can be arranged via separate .yml files under the repo’s .github/workflows/ directory.

Example: only run Python analysis script tests (say, under “scripts/”) when analysis scripts are changed. If Fortran code or Python interface scripts are changed, run other CI.

File .github/workflows/ci_scripts.yml

name: ci_scripts

on:
  push:
    paths:
      - "scripts/**.py"
      - .github/workflows/ci.yml
  pull_request:
    paths:
      - "scripts/**.py"
      - .github/workflows/ci.yml

jobs:

  linux:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout
    - uses: actions/setup-python
      with:
        python-version: '3.x'

    - run: pip install .
    - run: pip install flake8 mypy pytest

    - run: flake8
    - run: mypy

    - run: pytest

File: .github/workflows/ci.yml

name: ci

on:
  push:
    paths:
      - "**.f90"
      - "**.cmake"
      - "**/CMakeLists.txt"
      - ".github/workflows/ci.yml"
  pull_request:
    paths:
      - "**.f90"
      - "**.cmake"
      - "**/CMakeLists.txt"
      - ".github/workflows/ci.yml"

jobs:

  linux:
    runs-on: ubuntu-latest
    timeout-minutes: 5
    steps:
    - uses: actions/checkout
    - uses: actions/setup-python
      with:
        python-version: '3.x'

    - name: Install packages
      run: |
        sudo apt update
        sudo apt install --no-install-recommends gfortran libopenmpi-dev openmpi-bin

    - run: cmake -B build
    - run: cmake --build build
    - run: ctest --test-dir build -V

Matlab mustBeA is used in function argument validation to check that a variable is in one of multiple classes, instead of the single class coercion used by Matlab arguments block by default.

Simply create a file in the project directory “mustBeA.m”, or under private/mustBeA.m

function mustBeA(x, classes)
% for Matlab < R2020b
arguments
  x
  classes (1,:) string
end

mustBeMember(class(x), classes)

end

Matlab mustBeFile and mustBeFolder can fail to validate when the filename starts with a tilde “~”. Tilde is used by most terminal shells to indicate the user home directory. However, Matlab does not currently recognize tilde.

Workaround this issue with expanduser.m in the mustBe* call.

Example: myfun.m:

function myfun(A, B)
arguments
  A {mustBeA(A, ["string", "char"])}
  B (1,1) {mustBeNumeric}
end

...

end

A summary of public Windows Subsystem for Linux changes for the latest Windows Fast Ring build and recent builds is provided. A master listing of current build vs. Ring is also available.

Additional notes:

• Windows Subsystem for Linux release notes
• Windows Subsystem for Linux: About with link to issue trackers, presentations, etc.
• Microsoft Commandline Blog

Common web page / blog post applications where concealing text until the viewer clicks include:

• table of contents
• spoilers
• long details not all readers are interested in at that point in the article

This is implemented via the HTML5 details tag. This technique works for many Markdown-based sites such as GitHub (GitHub Issues click-to-reveal long debug text) and GitLab.

<details>
  <summary>click for spoilers</summary>

  <ul>
    <li>The season finale for Season 1 showed ...</li>
    <li>And season 2 opener revealed ...</li>
  </ul>
</details>

Example

IANA RFC8615 defines a “.well-known/” folder for web servers to put metadata fundamental to a web server’s organization, policies or contact information. Several popular files are seen under public website “https://example.invalid/.well-known/" directory.

keybase.txt

verify ownership of domain for Keybase.io

security.txt

security incident contact info

dnt-policy.txt

Do Not Track Policy statement

humans.txt

author information

The 2020 movie “The Midnight Sky” is based on the 2016 Lily Brooks-Dalton book Good Morning, Midnight. I customarily approach book-based films by reading the book first. This review is only about the book.

I found the character-oriented narrative quite compelling, with multiple characters having development and reflection. The only slight downside to the book is as typical in most fiction (including post-apocalyptic and science fiction), the radio communications and vehicle aspects of the book could have been described more accurately by having a technical reviewer. I think the author did a better than average approach to the radio comms, minus the glitches noted below. I compliment the author’s approach–these slight issues are endemic in fiction books. Contradictions I notice involved transportation and radios comms.

A gasoline engine that has a pull rope start is subsequently described as having a dead battery and therefore unable to start. In fact, it’s possible in some cases to improvise a pull start on small electric start engines. Since another similar vehicle is described as having electric start, this may have been an editing mistake (perhaps the final intent was to have both vehicles be electric start).

The author’s ham radio callsign is used by a character–cute! The author could have more specifically addressed LEO satellite comms window for simplex VHF comms. The characters could simply say VHF / UHF, as it’s uncommon to spell out the abbreviated terms. There are frequent references to RF sine waves, when actually random noise was seemingly implied.