Gadgetory

JIT is one of those newfangled business acronyms that's thrown around in board meetings and on news sites all the time but what is it what does it have to do with Android that's what we're gonna learn on today's episode of the android power-user so JIT sometimes pronounced JIT what is it well it stands for just-in-time it's always good to be on time right well what does it mean for that we got to go to logistics you ready for this one we'll keep it short in logistics supply and demand production lines assembly lines whatever you want to call it JIT is the concept of having inventory delivered just when you need it just-in-time if you're a manufacturer of widgets and you need some cogs well you don't want to have a whole bunch of cogs on hand because inventory is expensive warehouses to hold that inventory are expensive insurance to prevent or to make up for break-ins on those cogs is expensive so if you can cut down all of that inventory and get your stuff just in time well you're great unfortunately there are some drawbacks to that like what happens if there's a hurricane or flood or you don't have a reliable cog maker darn Cogswell well in that case you're gonna have problems on your production line but that's kind of where the JIT metaphor breaks down so what are we talking in terms of JIT and Android JIT in computers and let's face it androids are computers comes down to something that's sometimes referred to as dynamic translation essentially you're running your program right when you need it you're not really running it and that's where things get a little bit complicated so before we uncomplicated a a little background in computers computer development I'm a developer for my day job I write code all day long but the code that I write is all c-sharp net I've coded in other stuff I've coded in Pascal and Visual Basic in C and C++ and even in Java but they're all essentially the same thing they are a programming language it's somewhat easy to program in a programming language at least when compared to programming in native code native code is the code that programs are run in so if you want to run any application any program at all desktop tablet smartphone doesn't matter you have to run it in native code that's all computers know how to run his native code it wasn't written in native code it might have been written in objective-c or Java so how does it get from those over into native code the way that all works is something called compilation the process of compiling is essentially translating your code which is kind of human readable and easy to understand at least for geeks like me into something that's really complicated and hard for me to read but easy for a computer to read and to execute that's the key right there being able to actually execute or run the program or app downsides to compiling compiling takes time head on over to pocketnow.com look at the little comic i've got on that it's awesome though I don't necessarily like fencing laser tag during compiling you know what I'm talking about but compiling it takes time and there are limitations so let's step in the Wayback Machine and talk about Windows Mobile before it was called Windows Mobile way back then we had pda's running an operating system it was Windows CE II and on that OS we could install apps though back then they were called programs those programs came in various different formats and you had to know which one you needed to run it on your particular device C back then we had strong arm we had MIPS I think we even had a couple other processors out there each processor has advantages and disadvantages but they couldn't run each other's programs so as a developer you would write the code once in your common language whether that's a vbe or whatever and then you'd compile it but you'd compile it for each one of these processors so at the end of the day you'd end up with like four or five programs but they wouldn't be able to run except on one particular platform and well Windows Mobile or Pocket PC or whatever we called it back then there were lots of different manufacturers and each one kind of liked having their own different processor so you've had to have different executables for each processor kind of a pain in the neck especially for developers who essentially now have to compile it five times not cool so what does any of this have to do with Android after all Android apps are written in Java right oh yes they are but they're not running Java they're run in you guessed it machine code how do we get it from point A to point B and how come you don't have to pick from like five or six different versions of an app when you're going to the Play Store very good questions okay so the Play Store thing has a couple different answers first of all you really shouldn't see apps that aren't compatible with your device plain and simple the Play Store does a fairly good job at doing that sure you might see them but you won't be able to install them it's close and yes there are different versions of different apps for different platforms and screen resolutions and whatnot but we're not going to get into that today instead what we're going to talk about is something that Android does that's a little bit different you see it runs all of your apps in what's called a virtual machine again we're not going to talk too much about that today instead we're going to talk about something that happened well somewhat recently it's been a while but it didn't come around with the invent of Android when it was first released and it's called the JIT compiler or running in JIT in the compiler okay what does all that mean that's a lot of jargon and acronyms jit when applied computing means we're taking our uncompelled code that we as developers write we as developers publish to the Play Store our own websites some other market really doesn't matter and somehow it gets onto your phone once it's on your phone you need to run it well to be able to run it it has to be compiled compiling as we already discussed takes time that time translates into something that we like to call lag you push a button on the screen and it just sits there and waits for a while and thinks oh and then it does something that lag is just painful it's not enjoyable it's not fun it's not smooth and it's not fast so that's the only things kind of used to work they would be automatically compiled when you ran them now that sounds like just in time but it's not just in time or JIT was introduced into Android sometime ago and it really sped things up quite a bit because it would compile your code right when you want it to run it and not all of it just the stuff that you needed to be able to run and then it got kind of super smart and it started predicting what code you'd need to compile next or what code it would need to compile next for you to be able to run does any of this make sense let's back up so I have an app I install it on my phone or my tablet I go ahead and tap the icon what happens then is that app portions of it are dynamically compiled on the fly just enough to get me started once that's done then the rest is kind of pre compiled and put into cache yes that's kind of an oversimplification of how things work we do that quite a bit on Android power user but it gives you the idea just what you need is compiled just when you need it it's a lot faster and then in the background the other stuff is dynamically compiled and cached from when you need it it's very intelligent now what does this let us do let's back up for just a minute I may have an Android smartphone and an Android tablet and they may be running the same processor or I may be running an Android tablet and the next Android phone that comes out it might not be running a Snapdragon processor it might be running an intel possible but the Intel processor doesn't have the same codebase as that Snapdragon it's a different architecture what does that mean well in the Windows Mobile days that means every single app developer who has ever written an app for any version of Android has to now recompile their app and redistribute it for both the Snapdragon and the Intel processors it's a pain it's never gonna happen so all of this gets kind of muddled together and it would be painful so Intel essentially would never be able to make a processor that Android would run on unless they switched over to the Snapdragon architecture which they're just not gonna do that would mean that we'd all be relegated just a Snapdragon that's not to say Snapdragon isn't great it's just don't we want to be able to do other stuff don't we want that freedom as Android enthusiasts don't we want that freedom of course we do so the way Android is built all you have to do if you're Intel is rewrite Android not rewrite it but we compile it translate it make it run on your infrastructure on your architecture on your chips great once you have that done in yes that includes the operating system that includes drivers that includes all the apps that you need that are native apps run written in native code you've got to translate those but then all of the other apps that are run through this JIT compiler they're gonna work just fine why because once you get that translator working anything that's pre-written will run on anybody else's platform that's really the beauty of JIT that's why it's so amazing and we're not even living up to that potential yet so right now all we have to do is live with you know the increased speed the apps running just when you need them the saved memory the buttery smoothness we'll just have to make do with that but in future in the future will be able to support many different platforms and hopefully we'll see an Intel one that we can actually buy some time soon so that's the nuts and the bolts behind what this JIT does now there's something else involved there and it's called dalvik but that's going to be the topic for another episode of the Android power user if you like this kind of discussion make sure you give the video a big thumbs up if you haven't subscribed already make sure you hit the link at the end of the video so that you can be notified when we have new episodes not just of Android power user but other Android even Windows Phone and iPhone stuff as well we'll go ahead and let you know right there quick and easy if you'd like to discuss comment ask questions make sure you follow the link right down at the bottom of this if you're watching this on youtube so you can go over to the discussion at pocketnow.com that's where will we be having that for pocket now the Android power user I'm Joe Levi thanks for watching