Mauro, Thanks. I've read the scope and performance sections you've mentioned. Part of the problem comes from the often competing approaches of scientific/numerical computing and well-versed/structured programming practices. I have my hand in both pots at times. While global variables are viewed as horrible style by anyone with a formal education in programming science, it still lives on in glorious fashion (along with everything else Fortran 77 and Fortran 90) in modern scientific codes. I'm fine with migrating some legacy codes that use such global variable approaches to newer formats/styles. But, at the moment, I'm just trying walk before I run.
Nick On Saturday, November 19, 2016 at 11:51:41 AM UTC-6, Mauro wrote: > > Welcome to Julia! > > Without having read your post in detail, your example looks like your > using global variables to hold the state as you're not passing around > anything. Apart from bad style in general, in Julia this is also bad > for performance (read [1]). The compiler cannot work well with globals. > If you need them, declare their binding `const`. If you do need to use > globals from another module then you need to qualify them as a module > introduces a name-space, e.g. `MyModule.global1`. Also have you read > http://docs.julialang.org/en/release-0.5/manual/variables-and-scoping/? > > (Note that most discussion seems to have moved to > https://discourse.julialang.org/. If my answer didn't help, maybe post > there again. Although a shorter post might help to cater to people's > short attention span.) > > [1] http://docs.julialang.org/en/release-0.5/manual/performance-tips/ > > On Fri, 2016-11-18 at 11:22, Nicholas Mueschke <nmue...@gmail.com > <javascript:>> wrote: > > To start, I'm new to Julia and I'm trying things out to test Julia out > for > > some scientific/engineering applications. In particular, I'm working on > > moderate size projects, where they're big enough that I'll need more > than > > one file with code in it to stay organized (let's say anywhere from 5-50 > > files, 10s-100s of functions. However, I'm struggling to figure out an > > appropriate way to organize my code and ensure that the proper variables > > are in scope where they are needed. > > > > To start, I come from a Matlab/C#/C++/Fortran/Basic/Pascal/etc. > background > > and have been coding for long time, so I'm a little baffled by Julia's > > structure. > > > > Here's the basic description of my problem. I've got a collection of > > (sometimes large) 1D arrays. I'll define some starting values for these > > arrays and then I simply iterate on them and update the values in the > > arrays (basically I'm solving unsteady PDE problems). A very simple > > program structure would look something like this (thinking in terms of a > > functional programming approach in Matlab/C/Fortran,): > > > > > > > -------------------------------------------------------------------------------------------- > > > > module MyProjectModule > > > > # Include some files that have functions I need > > include("SetSomeProblemParameters.jl"); > > include("DeclareASetOfArrays.jl"); > > include("AssignInitialValuesToArrays.jl"); > > include("CheckSomeValuesInSomeArrays.jl"); > > include("CalculateSomeValuesBasedUponArrayValues.jl"); > > include("UpdateValuesOfArrays.jl"); > > include("WriteResultsToDisk.jl"); > > > > # Make main() visible > > export main > > > > > > main(NumberOfIterations) # This is the main entry point of the code > that > > performs a lengthy numerical calculation > > > > SetSomeProblemParameters() > > DeclareASetOfArrays() > > AssignInitialValuesToArrays() > > > > while (NumberOfIterations not reached) > > CheckSomeValuesInSomeArrays() > > CalculateSomeValuesBasedUponArrayValues() > > UpdateValuesOfArrays() > > > > NumberOfIterations++ > > end #while > > > > WriteResultsToDisk() > > > > end #main > > > > end MyProjectModule > > > -------------------------------------------------------------------------------------------- > > > > > > > > Simple, right? > > > > Question #1: If main entry point to run a calculation "main()" is a > > function, it gets its own variable workspace, right? Now, if I write a > > script (not a function) and use include("some_script.jl") with main(), > does > > Julia just inline that code within main()? In terms of scope, should > the > > script file be able to see all of the variables in the scope of main()? > In > > Matlab that would be true. In Fortran/C that wouldn't. I guess, I'm > not > > sure what scope implications there are for Julia script files. > > > > Question #2: If I've defined a bunch of functions as shown in the > > pseudocode above, what is the most performant way to have the large 1D > > arrays accessible within the scope of each function. As you can tell, > I'm > > trying to avoid writing functions that accept a long list of input > > parameters. The old Fortran solution is to simply make the arrays > global, > > so that each function can access them as needed. How terrible is that > idea > > within the Julia framework? Also, how can I even do that? I've tried > > writing a script (not a function) to declare a long list of global > > variables and then used include("DeclareGlobalVariables,jl) within my > main. > > But, when I return to main(), those variables do not show up in the > > workspace for main??? What am I missing? > > > > Question #3: I come from a VisualStudio IDE background, so I'm having > > trouble figuring out how to organize a Juila project. I'm trying out > Atom > > for my first Julia tests. For a project that's bigger than just a > script > > or a few functions, should I be defining a defining main entry point > > function within a module? Why Does Julia force modules to be added as > > packages so they can be loaded with the "using" command? That seems > > strange. Or, should I just write everything as a collection of files > with > > functions in them and not worry about modules? Simple REPL and one file > > Julia examples are everywhere. There are also large coding > > projects/libraries/utilities on github as examples, but I'm having > trouble > > figuring out the structure of these larger projects. I guess, I'm > > somewhere in between these two cases, where I'm just want to crunch some > > numbers, but I'm a little more complicated/sophisticated than the single > > file examples. What's the best way to proceed with such a project/file > > structure? > > > > Thanks in advance for any help. > > > > Nick >
