One big advantage over FreeFem is that it uses plain old Python to describe the problems instead of a domain-specific language. Matplotlib is used for plotting by default, so we get full Python power out of the box!
One downside is that its documentation is a Springer published PDF link.springer.com/content/pdf/10.1007%2F978-3-319-52462-7.pdf which is several years out-of-date (tested with FEnics 2016.2. Newbs. This causes problems e.g.: stackoverflow.com/questions/53730427/fenics-did-not-show-figure-nameerror-name-interactive-is-not-defined/57390687#57390687
system of partial differential equations are mentioned at: link.springer.com/content/pdf/10.1007%2F978-3-319-52462-7.pdf 3.5 "A system of advection–diffusion–reaction equations". You don't need to manually iterate between the equations.
On Ubuntu 20.04 as per fenicsproject.org/download/Before 2020-06, it was failing with:but they seem to have created the Ubuntu 20.04 package as of 2020-06, so it now worked! askubuntu.com/questions/866901/what-can-i-do-if-a-repository-ppa-does-not-have-a-release-file
sudo apt-get install software-properties-common
sudo add-apt-repository ppa:fenics-packages/fenics
sudo apt-get update
sudo apt-get install --no-install-recommends fenics
sudo apt install fenics
python3 -m pip install -u matplotlibE: The repository 'http://ppa.launchpad.net/fenics-packages/fenics/ubuntu focal Release' does not have a Release file. Ciro's Edict #6 cirosantilli.com content uploaded to ourbigbook.com/cirosantilli Updated 2025-04-24 +Created 1970-01-01
Managed to upload the content from the static website cirosantilli.com (OurBigBook Markup source at github.com/cirosantilli/cirosantilli.github.io) to ourbigbook.com/cirosantilli.
Although most of the key requirements were already in place since the last update, as usual doing things with the complex reference content stresses the system further and leads to the exposition of several new bugs.
The upload of OurBigBook Markup files to ourbigbook.com was done with the newly added OurBigBook CLI
ourbigbook --web option. Although fully exposed to end users, the setup is not super efficient: a trully decent implementation should only upload changed files, and would basically mean reimplementing/using Git, since version diffing is what Git shines at. But I've decided not to put much emphasis on CLI upload for now, since it is expected that initially the majority of users will use the Web UI only. The functionality was added primarily to upload the reference content.This is a major milestone, as the new content can start attracting new users, and makes the purpose of the website much clearer. Just having this more realistic content also immediately highlighted what the next development steps need to be.
Once v1.0 is reached, I will actually make all internal links of cirosantilli.com to point to ourbigbook.com/cirosantilli to try and drive some more traffic.
The new content blows up by far the limit of the free Heroku PostgreSQL database of 10k lines. This meant that I needed to upgrade the Heroku Postgres plugin from the free Hobby Dev to the 9 USD/month Hobby Basic: elements.heroku.com/addons/heroku-postgresql, so now hosting costs will increase from 7 USD/month for the dyno to 7 + 9 = 16 UDS/month. After this upgrade and uploading all of cirosantilli.com to ourbigbook.com, Heroku dashboard reads reads:so clearly if we are ever forced to upgrade plans again, it means that a bunch of people are using the website and that things are going very very well! Happy how this storage cost turned out so far.
One key limitation found was that Heroku RAM memory is quite limited at 512MB, and JavaScript is not exactly the most memory economical language out there. Started investigation at: github.com/ourbigbook/ourbigbook/issues/230 Initially working around that by simply splitting the largest files. We were just on the verge of what could be ran however luckily, so a few dozen splits was enough, it managed to handle 70 kB OurBigBook Markup inputs. So hopefully if we manage to optimize a bit more we will be able to set a maximum size of 100 kB and still have a good safety margin.
Filter graphs are a thing of great beauty. What an amazingly obscure domain-specific language, but which can produce striking results with very little!!!
A quick example from stackoverflow.com/questions/59551013/how-to-generate-stereo-sine-wave-using-ffmpeg-with-different-frequencies-for-eac/77730492#77730492 illustrates some of the fundamentals:
ffplay -autoexit -nodisp -f lavfi -i '
sine=frequency=500[a];
sine=frequency=1000[b];
[a][b]amerge, atrim=end=2
' +--------+
[sine=frequency=500]--->[a]-->| |
| amerge |-->[atrim]-->[output]
[sine=frequency=1000]-->[b]-->| |
+--------+So we see the following syntax patterns:
sine,amergeandatrimare filterssine=frequency=500: the first=says "araguments follow";: separates statements[a],[b]: sets the name of an edge,: creates unnamed edge between filters that have one input and one output
A list of all filters can be obtained ith:and parameters for a single filter can be obtained with:Related question: stackoverflow.com/questions/69251087/in-ffmpeg-command-line-how-to-show-all-filter-settings-and-their-parameters-bef
ffmpeg -filtersffmpeg --help filter=sineTODO dump graph to ASCII art? trac.ffmpeg.org/wiki/FilteringGuide#Visualizingfilters mentions a
-dumpgraph option, but haven't managed to use it yet.Bibliography:
- ffmpeg.org/ffmpeg-filters.html official documentation
- trac.ffmpeg.org/wiki/FilteringGuide some handy tips from the FFMpeg Wiki
A field can be seen as an Abelian group that has two group operations defined on it: addition and multiplication.
And then, besides each of the two operations obeying the group axioms individually, and they are compatible between themselves according to the distributive property.
Examples:
A recreational computer simulation!
Although Ciro Santilli is a big fan of plaintext files and of Vim, not so for games. Games must be easy to understand since they are just a toy.
Tilesets to the rescue!
The opposite of freedom of speech.
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