Tutorial of workdone3/1/2023 ![]() ![]() Now start a fresh session, load the package (you'll need that push!(LOAD_PATH, "DemoPkg/") again), and time it: julia> tstart = time() DemoPkg.f(5) tend=time() tend-tstart Precompile(f, (Int,)) # THE CRUCIAL ADDITION! Here we'll choose precompile: julia> open("DemoPkg/src/DemoPkg.jl", "w") do io Precompile(f, (Int,)), if we don't need the output of f(5) but only wish to trigger compilation of f for an Int argument. All we need to do is add a single line to the module definition: eitherį(5), which executes f while the package is being precompiled (and remember, execution triggers compilation, the latter being our actual goal) We can save some of this time by precompiling it and saving the result to disk. The extra cost for the first invocation is the time spent compiling the method. Julia> tstart = time() DemoPkg.f(5) tend=time() tend-tstartīut the second one (in the same session) is much faster: julia> tstart = time() DemoPkg.f(5) tend=time() tend-tstart If we load the package, the first call DemoPkg.f(5) takes some time: julia> push!(LOAD_PATH, "DemoPkg/") Julia> open("DemoPkg/src/DemoPkg.jl", "w") do ioĪfter executing this, you can open the DemoPkg.jl file to see what f actually looks like. You can copy/paste the following into Julia's REPL (be aware that it creates a package directory DemoPkg inside your current directory): julia> using Pkg Pkg.generate("DemoPkg") We'll start with a package that we can define in a few lines (thanks to Julia's metaprogramming capabilities) and depending on very little external code, but which has been designed to have measurable latency. To motivate this series, let's start with a simple demonstration in which adding a single line to a package results in a five-fold decrease in latency. Because type inference takes time, this can reduce the latency for the first use of methods in the package. Precompilation in its most basic form happens nearly automatically, but with a bit of manual intervention developers also have an opportunity to save additional information: partial results of compilation, specifically the type inference stage of compilation. During precompilation, Julia writes module, type, and method definitions in an efficient serialized form. output that occurs after updating packages on Julia 1.6. We'll focus on precompilation, julia> using SomePkg The primary focus of this series is to explore the opportunity to reduce the cost of compilation. In very rough terms, using SomePkg loads types and/or method definitions, after which calling SomePkg.f(args.) forces SomePkg.f to be compiled (if it hasn't been already) for the specific types in args. ![]() ![]() ![]() (You do not need to read the previous blog post to understand this one.) In this series, it is assumed that invalidations are not a dominant source of latency. Julia's dynamic nature also makes it vulnerable to invalidation and the subsequent need to recompile previously-compiled code this topic has been covered in a previous blog post, and that material will not be rehashed here. Most of Julia's latency is due to code loading and compilation. Sources of latency, and reducing it with precompile This particular installment covers background material–some key underlying concepts and structures–that will hopefully be useful in later installments. This is the inaugural post in a short series devoted to the topic of what package developers can do to reduce latency for their users. While a lot of work (and success) has gone into reducing latency in Julia 1.6, users and developers will naturally want to shrink it even more. This is sometimes called "time to first plot," although it applies to far more than just plotting. It just gives the time that work requires.One of the main foci of development during Julia 1.6 has been to reduce latency, the delay between starting your session and getting useful work done. In other words he does 20 joule work in 6 seconds.Īmount of power does not show the amount of work done. The unit of the power from the equation given above, joule/s, however, we generally use the unit of power as watt.Įxample: Find the power of the man who pushes the box 8m with a force of 15N in a 6seconds. The shorter the time the more power full the man. Thus, the man doing same work in 5 seconds is more power full. Say one of them does the work in 5 seconds and the other does in 8 seconds. For example, same work is done by two different people with different time. However, power just shows us the time that the work requires. They think that more power full machine does more work. It can be misunderstood by most of the students. Power is the rate of work done in a unit of time. ![]()
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