[WIP] Feature/math guide #192
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| The arena does not call destructors for objects stored in arena. | ||
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| ## Autodiff memory |
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This section seems a bit incomplete. I would also expect info on when to put a vari on certain stack.
| Substitution Failure Is Not An Error is the preferred way to define | ||
| function implementations in Stan. |
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| Substitution Failure Is Not An Error is the preferred way to define | |
| function implementations in Stan. | |
| Overloads using "Substitution Failure Is Not An Error" are the preferred way to define | |
| different function implementations for different input types in Stan Math. |
| function implementations in Stan. | ||
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| Function argument lists are fully templated, and then template meta-programs | ||
| are used to define which definitions are visible at argument lookup. |
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| are used to define which definitions are visible at argument lookup. | |
| are used to define which overloads can be specialized for particular argument types. |
| versions. This can happen when multiplying the values/adjoints of an AOS | ||
| autodiff type against other matrices. | ||
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| It is not safe to use `.noalias()` with the AOS value/adjoint expressions. |
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I'm not sure, but I believe it exploded when I did it before. When @SteveBronder did this he added some if statements so the noalias code only ran for SOA. I forget where it was though (I thought multiply but when I looked it wasn't there).
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| ### Multiple argument scalar types | ||
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| Pretend for a minute that |
| As an aside, in order to get the actual vector result, Eigen defines the | ||
| `.eval()` operator, so `c.eval()` would return an actual `Eigen::VectorXd`. | ||
| Similarly, Math defines the `eval` function which will evaluate an Eigen | ||
| expression and forward anything that is not an Eigen expression. |
Co-authored-by: Tadej Ciglarič <tadej.c@gmail.com>
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Judging from your comments @t4c1 you like the longer document? So it's fair to count that as a vote to just finish the longer thing instead of a cheat-sheet style doc? |
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Well the longer one will be more useful for new devs. Also it looks like 90% finished to me. |
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| The title contans "Current State" to emphasize that if any information here is | ||
| out of date or any advice does not work, it should be reported as a bug (the | ||
| [example-models](https://github.com/stan-dev/example-models)). |
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[todo] move this over to the math site.
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fyi working on writing some stuff up based on this as well |
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@SteveBronder feel free to edit here or move this to where you want to work on it. Based on what Tadej said, I'm thinking ditch the cheat sheet (but I'll just leave it in for copy-pasting convenience) |
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Sounds great. @seantalts and I went through a whole lecture at StanCon Helsinki on how to add a function to the math library. And we didn't even cover all the doc we had written then. So this is a big problem. I also want to say that as long as what's there is correct, it doesn't matter if it's not 100% complete---it'll be an improvement on what we have. |
…ple-models into feature/math-guide
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The new place to work on this is stan-dev/math#2350. I merged the comments from this thread into that. |
My first attempt was to write intro docs for all the new stuff in Stan. That started getting long and I was barely making it anywhere so I gave up. Rendered attempt is here
Then I tried to write a cheat sheet for all the new stuff in Stan. The idea being that things only needed roughly documented examples and a few words. It's still crazy long, not sure it will fit on a cheat sheet. Rendered cheat sheet is here
Now I am thinking that my best chance of finishing something is an "anatomy of a Stan function" document. For this, the goal would be to take an existing function and explain the file structure, tests, and add verbal descriptions of all the little different things inside it (and leave the technical description to the doxygen and examples to other functions).
Anyway putting this stuff up to share, not looking for merge.