Fortran is back on the top 20 TIOBE index list • Hacker News Board

Re: Fortran is back on the top 20 TIOBE index list

#41

Post by enriquto » Thu, Apr 08, 2021, 5:32 PM UTC

leephillips wrote: post #38

enriquto wrote: post #37

Earlier quoted context omitted.

Can you expand a bit on the need for "types" in numerical computation? They sort of seem like overkill to me. The only types I use are float and double, but I could really do with just doubles. OK, admittedly I also need complex numbers (two floats) and ad numbers (however they are represented, typically by two floats also). But that's it . They are numbers after all, associative and commutative. The "dispatch paradi…

I think I have a pretty good answer to your question in this article: https://lwn.net/Articles/834571/ It’s not that other types are “needed”, but that they let you do some pretty powerful things with surprising ease. And the nice thing is that in Julia, you can ignore them. You can just compute with floats or doubles as if the type system doesn’t exist. But it’s there in case you would like, for example, to apply th…

Thanks for this article, it's really well written and engaging.

But here, I cannot resist:

> You can just compute with floats or doubles as if the type system doesn’t exist.

Except when you can't! I want to plot a stupid array of floats. Yet it takes 10 seconds because it is juggling useless types around. A complex type system may be a nice thing to have, if you really want it, but it is definitely not "free", and it always involves serious compromises that make other things impossible or very cumbersome. I would like an option like --type=float in the interpreter that assumed that all numbers are of that type and ran extremely fast.

Re: Fortran is back on the top 20 TIOBE index list

#42

Post by leephillips » Thu, Apr 08, 2021, 5:49 PM UTC

enriquto wrote: post #41

leephillips wrote: post #38

Earlier quoted context omitted.

I think I have a pretty good answer to your question in this article: https://lwn.net/Articles/834571/ It’s not that other types are “needed”, but that they let you do some pretty powerful things with surprising ease. And the nice thing is that in Julia, you can ignore them. You can just compute with floats or doubles as if the type system doesn’t exist. But it’s there in case you would like, for example, to apply th…

Thanks for this article, it's really well written and engaging. But here, I cannot resist: > You can just compute with floats or doubles as if the type system doesn’t exist. Except when you can't! I want to plot a stupid array of floats. Yet it takes 10 seconds because it is juggling useless types around. A complex type system may be a nice thing to have, if you really want it, but it is definitely not "free", and it…

I’m glad you liked the article. Obviously the 10 second or so of precompilation time is a big issue for you. I guess I have no further suggestions about that other than to suggest again to look at creating sysimages (learning how to do this is on my to-do list).

Re: Fortran is back on the top 20 TIOBE index list

#43

Post by enriquto » Thu, Apr 08, 2021, 6:14 PM UTC

leephillips wrote: post #42

enriquto wrote: post #41

Earlier quoted context omitted.

Thanks for this article, it's really well written and engaging. But here, I cannot resist: > You can just compute with floats or doubles as if the type system doesn’t exist. Except when you can't! I want to plot a stupid array of floats. Yet it takes 10 seconds because it is juggling useless types around. A complex type system may be a nice thing to have, if you really want it, but it is definitely not "free", and it…

I’m glad you liked the article. Obviously the 10 second or so of precompilation time is a big issue for you. I guess I have no further suggestions about that other than to suggest again to look at creating sysimages (learning how to do this is on my to-do list).

> I’m glad you liked the article.

I was particularly "seduced" by the idea of using a standard ODE solver directly on quaternions. Having worked in the smoothing of 3D camera trajectories the last year, I would have definitely loved to know that at the time!

Re: Fortran is back on the top 20 TIOBE index list

#44

Post by jonniedie » Fri, Apr 09, 2021, 2:22 PM UTC

enriquto wrote: post #37

leephillips wrote: post #36

Earlier quoted context omitted.

The type system and dispatch paradigm provide a powerful method of code and project organization, and facilitate a type of code reuse that you don’t get with Fortran: the ability to pull other people packages into my project and use their types and methods. That’s one thing. EDIT: Also, having a REPL, and a nice one, is a big deal.

Can you expand a bit on the need for "types" in numerical computation? They sort of seem like overkill to me. The only types I use are float and double, but I could really do with just doubles. OK, admittedly I also need complex numbers (two floats) and ad numbers (however they are represented, typically by two floats also). But that's it . They are numbers after all, associative and commutative. The "dispatch paradi…

Some other nice things that come from having a type system for numerical work:

- Forward mode automatic differentiation. Having a type system that allows `Dual` numbers to pass through your algorithm, simulation, or whatever means you can calculate derivatives, gradients, jacobians, and hessians efficiently (for small problems) and accurately without having to change any of your code. There are so many times where I say “hey, I wonder what the sensitivity of my simulation output to this input parameter is” and it’s really nice to be able to answer that question with one line of code.

- Unitful numbers. It’s really nice to be able to pass numbers with units through a simulation (little to no performance penalty!) to make sure everything checks out in that respect.

- Uncertainty. Both Measurements.jl and MonteCarloMeasurements.jl provide numbers that propagate (linear and nonlinear, respectively) uncertainty as the pass through calculations. Want to see how uncertainty in a parameter propagates through a calculation? Just change that one parameter to an uncertain number and let it run through your algorithm as-is and it will spit out an answer with uncertainty bounds on the other side.

These are just a few examples of the stuff I use it for in my everyday work. Having a full type system for numerical work is one of those things that seems silly before you use it, but once you do, you wonder how you got by without it before.

EDIT: BTW, these are just examples of numerical types. Sending specialized array types through a your code is also a thing. For example, if you have a `Diagonal` type matrix and you send it to an eigenvalue solve, it just pulls the elements from the diagonal without wasting any time trying to calculate anything. Or there are things like ComponentArrays.jl (full disclosure, I wrote this library), that let you pass arbitrarily deep structured information through a differential equation or optimization solver for much cleaner and more readable code than just indexing into a plain vector like you would usually have to do. And you can even put your weird numerical types inside of the weird array types and just send it on through.