Lecture 3 : Optimization 1

Some Julia Package Stuff

Let's create a julia package!

]
(@v1.8) pkg> add PkgTemplates

julia> using PkgTemplates

help?> Template

julia> t = Template(user = "floswald", interactive = true)
Template keywords to customize:
[press: d=done, a=all, n=none]
   [ ] authors
   [ ] dir
   [ ] host
   [ ] julia
 > [ ] plugins

julia> t("MyNewPackage")
[ Info: Running prehooks
[ Info: Running hooks
...suppressed output...
[ Info: New package is at /Users/74097/.julia/dev/MyNewPackage

• Great! Now let's open VSCode in that location and make some changes.

module MyNewPackage

mutable struct MPoint
    x::Number
    y::Number
end

import Base.:+

+(a::MPoint,b::MPoint) = MPoint(a.x + b.x, a.y + b.y)

end   # module

• Now, we could just execute active file in REPL in VSCode, or indeed, type in the REPL include("src/MyNewPackage.jl"):

julia> include("src/MyNewPackage.jl")
Main.MyNewPackage

• Now we can test the code in the REPL.

• Notice, importantly, each time you want to see the effects of changing your code, you have to replace the module via include("src/MyNewPackage.jl").

julia> include("src/MyNewPackage.jl")
WARNING: replacing module MyNewPackage.

• Let's add a test for our + method in the test folder:

@testset "MyNewPackage.jl" begin
    a = MyNewPackage.MPoint(3,5)
    b = MyNewPackage.MPoint(1,2)
    @test a + b isa MyNewPackage.MPoint
    p = a + b
    @test p.x == a.x + b.x
    @test p.y == a.y + b.y
end

• Run the tests from REPL in Pkg mode: ]; test

• This works, but it involves one extra step that we need to do manually. Small steps add up! So let's try to improve on that.

• Let's tell the package to add Revise.jl: ]; add Revise.

• Shut down and restart VScode in same folder.

• Before anything else, type using Revise. Then type using MyNewPackage.

• Let's add a new function now.

-(a::MPoint,b::MPoint) = MPoint(a.x - b.x, a.y - b.y)

• Don't replace the module via include("src/MyNewPackage.jl"). Instead, just save the file and go back to REPL.

julia> a = MyNewPackage.MPoint(3,4)
MyNewPackage.MPoint(3, 4)

julia> b = MyNewPackage.MPoint(99,100)
MyNewPackage.MPoint(99, 100)

julia> a - b
MyNewPackage.MPoint(-96, -96)

• 🎉

Debugging A Package

• Debugging simple scripts or packages is the same workflow.

• Let's add another function. An economic model of sorts:

function econ_model(; startval = 1.0)
    # make an Mpoint
    x = MPoint(startval, startval-0.5)
    # ... and evaluate a utility function
    MPoint(log(x.x),log(x.y))
end

• Make sure to try out that it works.

julia> MyNewPackage.econ_model()
MyNewPackage.MPoint(0.0, -0.6931471805599453)

• Ok great. Now what about that? Try it out!

julia> MyNewPackage.econ_model(startval = 0.3)

• Good. Let's pretend we don't know what's going on and we need to investigate this function.

1. Add println statements.

2. Add @debug statements. then attaching a logger with

using Logging
debug_logger = ConsoleLogger(stdout, Logging.Debug)
global_logger(debug_logger)  # turns on logging of @debug messages

3. Use an actual debugger to step through our code.

   1. VSCode exports by default the @enter macro. type: @enter MyNewPackage.econ_model(startval = -0.3)

   2. click on teh play symbol. program hits an error.

   3. set a break point just before

   4. click on replay.

Some Julia-Bootcamp stuff

Optimization, Finally!

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Last modified: November 04, 2024. Website built with Franklin.jl and the Julia programming language.