82 lines
5.1 KiB
Plaintext
82 lines
5.1 KiB
Plaintext
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%p
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While trying to figure out what i am coding i had to attack this storage format before i wanted to. The
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immediate need is for code dumps, that are concise but readable. I started with yaml but that just takes
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too many lines, so it’s too difficult to see what is going on.
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%p
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I just finished it, it’s a sort of condensed yaml i call sof (salama object file), but i want to take the
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moment to reflect why i did this, what the bigger picture is, where sof may go.
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%h3#program-lifecycle Program lifecycle
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%p
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Let’s take a step back to mother smalltalk: there was the image. The image was/is the state of all the
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objects in the system. Even threads, everything. Absolute object thinking taken to the ultimate.
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A great idea off course, but doomed to ultimately fail because no man is an island (so no vm is either).
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%h4#development Development
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%p
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Software development is a team sport, a social activity at it’s core. This is not always realised,
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when the focus is too much on the outcome, but when you look at it, everything is done in teams.
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%p
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The other thing not really taken into account in the standard developemnt model is that it is a process in
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time that really only gets jucy with a first customer released version. Then you get into branches for bugs
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and features, versions with major and minor and before long you’r in a jungle of code.
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%h4#code-centered Code centered
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%p
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But all that effort is concentrated on code. Ok nowadays schema evlolution is part of the game, so the
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existance of data is acknowledged, but only as an external thing. Nowhere near that smalltalk model.
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%p
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But off course a truely object oriented program is not just code. It’s data too. Maybe currently “just”
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configuration and enums/constants and locales, but that is exactly my point.
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%p
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The lack of defined data/object storage is holding us back, making all our programs fruit-flies.
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I mean it lives a short time and dies. A program has no way of “learning”, of accumulating data/knowledge
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to use in a next invocation.
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%h4#optimisation-example Optimisation example
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%p
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Let’s take optimisation as an example. So a developer runs tests (rubyprof/valgrind or something)
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with some output and makes program changes accordingly. But there are two obvious problems.
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Firstly the data is collected in development not production. Secondly, and more importantly, a person is
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needed.
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%p
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Of course a program could quite easily monitor itself, possibly over a long time, possibly only when
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not at epak load. And surely some optimisations could be automated, a bit like the O1 .. On compiler
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switches, more and more effort could be exerted on critical regions. Possibly all the way to
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super-optimisation.
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%p
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But even if we did this, and a program would improve/jit itself, the fruits of this work are only usable
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during that run of that program. Future invocations, just like future versions of that program do not
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benefit. And thus start again, just like in Groundhog day.
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%h3#storage Storage
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%p
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So to make that optimisation example work, we would need a storage: Theoretically we could make the program
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change it’s own executable/object files, in ruby even it’s source. Theoretically, as we have no
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representation of the code to work on.
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%p
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In salama we do have an internal representation, both at the code level (ast) and the compiled code
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(CompiledMethod, Intructions and friends).
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%h4#storage-format Storage Format
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%p
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Going back to the Image we can ask why was it doomed to fail: because of the binary,
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proprietary implementation. Not because of the idea as such.
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%p
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Binary data needs either a rigourous specification and/or software to work on it. Work, what work?
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We need to merge the data between installations, maintain versions and branches. That sounds a lot like
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version control, because it basically is. Off course this “could” have been solved by the smalltalk
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people, but wasn’t. I think it’s fair to say that git was the first system to solve that problem.
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%p
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And git off course works with diff, and so for a 3-way merge to be successful we need a text format.
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Which is why i started with yaml, and which is why also sof is text-based.
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%p The other benefit is off course human readability.
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%p
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So now we have an object file * format in text, and we have git. What we do with it is up to us.
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(* well, i only finished the writer. reading/parsing is “left as an excercise for the reader”:-)
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%h4#sof-as-object-file-format Sof as object file format
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%p
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Ok, i’ll sketch it a little: Salama would use sof as it’s object file format, and only sof would ever be
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stored in git. For developers to work, tools would create source and when that is edited compile it to sof.
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%p
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A program would be a repository of sof and resource files. Some convention for load order would be helpful
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and some “area” where programs may collect data or changes to the program. Some may off course alter the
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sof’s directly.
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%p
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How, when and how automatically changes are merged (via git) is up to developer policy . But it is
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easily imaginable that data in program designated areas get merged back into the “mainstream” automatically.
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