So you have to have some kind of order in here. So you put some position ordering and saying if you are sitting in even position, you're the first to pick the left one, if you are putting an odd position, you're supposed to pick the right one. So assume I go -- it's like sometimes you try to cross each other on the road and you go into them and say oops, or you both say oops, sorry, [UNINTELLIGIBLE] You get into a situation that you try to go something, both you start to move a little bit and then do that and you keep doing that forever and ever, doing it, right. Assume I am in a place that I actually want to put two ATMs or four ATMs next to each other. Or only one access at a time. You can say instead of doing a method, you can just synchronize account and all those things happen synchronously within that block. Or you have interface called [? You don't take in arbitary order. Copyright © 2004 John Wiley & Sons, Ltd. parallel and distributed programming languages, on it, ?] Or you can actually have running parallel. ), Learn more at Get Started with MIT OpenCourseWare, MIT OpenCourseWare makes the materials used in the teaching of almost all of MIT's subjects available on the Web, free of charge. We ensured [UNINTELLIGIBLE] that this mutual exclusion. And create an ATM in here, and you will make the ATM run. Then you go and say OK, I want to run parallel. So it might just look hits equals hits plus 1 and hits equals hits plus 1 on the cycle. Lecture Notes and Video Doesn't have to [? You can have three different machines running, A, B and C all the time. Persistent data structures keep the old state together with the modification. So I assume I had this program like that. So, concurrency and parallelism are important concepts in comparison beyond what we are doing in here. ?] So this is a problem with atomacity. This post by the Bifurcan Project compares different libraries that implement persistent data structures. The more I learn about multi-threaded programming, the harder it gets. Copying before modifying works best for workloads consisting of multiple reads and few writes. Your support will help MIT OpenCourseWare continue to offer high quality educational resources for free. Download the video from iTunes U or the Internet Archive. But keep these issues in my mind when you are writing parallel programs. PROFESSOR: OK, you want to check also. In one summer I was working on their LAN manager and network manager, and there's a bug that after you run the network manager for some time it just freezes. In parallel things actually, you can do parallel IO and you can do a lot cool stuff in here. Authors: Justin T. Maris, Aaron W. Keen, Takashi Ishihara, Ronald A. Olsson, Keywords: load balancing, Concurrent programming, synchronization mechanisms, cooperative multithreading, parallel and distributed programming languages. Basically, it's almost a software [? Also, before you write it out, you read the balance in the other interleaving, you've got the balance as 100, and you do the plus as 10. » So what might happen in this case? Before you go there, one interesting thing is this is just a problem with all parallel programs. That's not a nice behavior to have if you are running your network. So here's another thing we want to do. Also, it allows you to coordinate actions among shared space, basically. I'm just going to talk about concurrent programming here. Once in a while voila. So what went wrong? So the problem with race conditions is the minute you put your debug, or put any debugging things, race conditions goes away. So another thing that's called starvation. And you get the balance in here. Type the account ID. And you have no idea why it happened. If you want to withdraw or deposit. So that's not nice, because if you've got the balance you should be able to get that. PROFESSOR: [UNINTELLIGIBLE PHRASE]. Because the minute you do any instrumentation, the [? Why do you want concurrent programming? So this is, you have to sometime do some changes to basically make the program work like this. Functional programming appeals to many of us for reasons other than these practical considerations: ... because I think this metaphor cuts exactly the opposite direction ... on 8 cores by adding a handful of lines to a program" tells me that Haskell is extremely good at letting you expose the concurrent structures of your problem domain. It's not that important. Are we happy? Because at some point people have to coordinate and take that parallel computation. So you arrive home, look in the fridge, no milk. So in here, what you can do is, in the program you can associate some kind of a rank, and when you put in account, you put the rank to the account number. Another thing is, of course, what I point out to have some kind of ordering. Because your program might not fit into this nice ordering a lot of times, and then sometimes you realize that you had locked something and at that time it's too late when you realize it. Second way to solve that is this, and you say OK. So, what's concurrency? You take the password, if it's wrong you throw exception. Then you treat the balance as 100. So in the next lecture, we will switch from Java to C-C , I guess using MPI primitives in here. Over a million developers have joined DZone. PROFESSOR: Not statically. Cars on the bridge going in the same direction ⇒can cross 2. Why do we need a volatile variable instead of a normal variable? That's the entire reason that we are still doing sequential programming and this is entire reason that multiple people are looking at it in a very -- people are scared because writing and getting concurrent program right is probably an order of magnitude harder than trying to get sequential programs right. How can we deal with this one? AUDIENCE: There are two ways of doing it. Courses PROFESSOR: So, the next part, today's going to be about concurrent programming. Now, inside I want to synchronize for Alyssa. Here workers are specialized for certain tasks opposite to the previous equally created workers; Advantages: Better locality Quality of Service management. I can do that. Download files for later. So good example. There I am holding Ben's account. Because the compiler puts a [? If you look at what happened in activity trace, so we print 100 in here.

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