WEBVTT 00:05.410 --> 00:11.170 So, guys, now in this lecture video, we will going to implement producer consumer problem statement. 00:11.320 --> 00:17.440 So all the codes that is related to producer consumer can be found in this code directory path and the 00:17.440 --> 00:23.860 file which represents an assignment into which we will going to write a code is this file that is assignment 00:23.860 --> 00:25.870 producer consumer on Q dot C. 00:26.080 --> 00:26.920 Right? 00:26.920 --> 00:32.920 So since the producer consumer are the threads which needs to act on a common resource, that particular 00:32.920 --> 00:33.850 resource is nothing. 00:33.850 --> 00:36.280 But we have taken that as a queue. 00:36.490 --> 00:42.490 So the queue data structure is implemented by these source file that is Q, dot C and Q dot H. 00:42.670 --> 00:48.850 We will going to use these files in the assignment and compile Dot as such is a shell script that compiles 00:48.850 --> 00:51.970 your entire assignment and create an executable exe. 00:52.390 --> 00:56.290 You simply need to run this executable in order to test your code. 00:56.320 --> 00:57.100 Right? 00:59.090 --> 01:03.500 So this is the assignment file into which we will going to write a code. 01:03.680 --> 01:07.790 So now let us understand the problem statement in little bit detail. 01:07.820 --> 01:14.120 So what we will going to do is that in our program we will have our resource which is represented by 01:14.120 --> 01:14.840 a data structure. 01:14.840 --> 01:22.100 Q Right, so this is the common resource which needs to be accessed by producer and consumer threads. 01:22.460 --> 01:26.600 We will going to create a program in which there will be two consumer threads. 01:26.630 --> 01:31.310 The name of the two consumer thread is Tc1 and Tc2, right? 01:31.310 --> 01:37.220 And as the name suggests, these are consumer threads, meaning that both these threads has the objective 01:37.220 --> 01:40.850 to remove an element from the queue until the queue is empty. 01:40.880 --> 01:41.750 Right. 01:42.020 --> 01:47.780 Then in our program we will going to launch two more threads which are called producer threads. 01:47.780 --> 01:51.110 So the name of the threads is tp1 and tp2. 01:51.110 --> 01:57.260 And the objective of the producer threads is to create an element and push it into the queue until the 01:57.260 --> 01:58.550 queue is full. 01:58.550 --> 01:59.420 Right? 01:59.540 --> 02:04.640 So you can see the job of the producer and consumer threads is exactly opposite to each other. 02:04.940 --> 02:11.240 Then queue is a common data structure which is being acted upon by consumer and producer threads. 02:11.240 --> 02:15.590 Therefore queue has condition variable and a mutex. 02:15.590 --> 02:16.340 Right. 02:19.040 --> 02:25.550 We already know that mutex is always a property of the resource that is being shared by the threads 02:25.550 --> 02:30.140 and condition variable we have taken in this case as a property of the queue. 02:30.170 --> 02:31.010 Right. 02:32.930 --> 02:40.430 All the threads which are competing to get an access over the shared resource queue will be blocked 02:40.460 --> 02:43.810 on this condition variable if the queue is not available. 02:43.820 --> 02:44.630 Right. 02:45.350 --> 02:51.920 So if you happen to take a look at the implementation of this queue, I will show you that while you 02:51.920 --> 02:52.940 open the file queue. 02:52.970 --> 02:54.260 Dot h. 02:55.860 --> 03:00.060 You will see that this is the data structure which represents the queue. 03:00.060 --> 03:03.650 And this data structure has a mutex and a condition variable. 03:03.660 --> 03:04.440 Right. 03:06.480 --> 03:12.450 And note that the default size of the queue is five, meaning that the maximum size of the queue cannot 03:12.450 --> 03:13.890 grow beyond five. 03:13.920 --> 03:19.860 We will going to discuss how to make use of this queue library in our program in order to implement 03:19.860 --> 03:22.170 our producer consumer problem statement. 03:22.560 --> 03:28.950 So now we know that in our program we need to launch two consumer threads and two producer threads and 03:28.950 --> 03:35.370 we have a common data source which is queue, which all the four threads would compete to get an access, 03:35.400 --> 03:36.030 right? 03:36.060 --> 03:41.160 These slides, which represents the problem statement have been attached in the resource section so 03:41.160 --> 03:45.570 that you can refer to the problem statement and attempt the solution by your own. 03:46.100 --> 03:49.590 Now let us discuss what exactly the problem statement is. 03:49.610 --> 03:55.040 So we will going to write a program which launches four threads to consumer threads and two producer 03:55.040 --> 03:55.820 threads. 03:56.060 --> 03:59.570 And you may create these threads in the joinable mode. 03:59.600 --> 04:06.210 Right now, all these four threads act on a shared resource which is nothing but a queue of integers. 04:06.230 --> 04:10.550 So you need to create a queue which store the integers as an element. 04:10.700 --> 04:15.080 Producer thread produce a random integer and add it to a queue. 04:15.110 --> 04:18.350 Whereas consumer threads remove an integer from the queue. 04:18.380 --> 04:19.160 Right. 04:19.160 --> 04:21.710 And the maximum size of the queue is five. 04:21.740 --> 04:23.360 This we have already discussed. 04:24.230 --> 04:28.840 So this is the overview of the problem statement that we will going to resolve. 04:28.850 --> 04:35.360 And also our problem statement has certain constraints which you need to implement or you need to respect. 04:35.780 --> 04:40.220 So while writing a solution, you need to implement the following constraints as well. 04:40.310 --> 04:45.810 The first constraint says that when produce a thread, produce an element and add it to the queue. 04:45.840 --> 04:50.580 The producer thread does not release the queue until the queue is full. 04:50.610 --> 04:55.320 That is, producer thread releases the queue only when the queue is full. 04:55.350 --> 04:56.220 Right. 04:56.250 --> 05:01.440 So producer thread keep on adding element to the queue until the queue is full. 05:02.100 --> 05:07.110 Once the queue is full only then the producer thread actually releases the queue. 05:07.350 --> 05:13.110 Similarly, when consumer thread consume an element from the queue, it consumes the entire queue and 05:13.110 --> 05:16.050 do not release the queue until the queue is empty. 05:16.050 --> 05:16.890 Right. 05:16.920 --> 05:23.250 And the point number three says that consumer thread signals the producer thread when the queue is exhausted 05:23.250 --> 05:27.780 and producer thread signals the consumer thread when the queue is full. 05:27.810 --> 05:33.300 So you can see that there is bidirectional communication between consumer threads and producer threads. 05:33.330 --> 05:39.960 The consumer thread signals the producers, whereas producer thread signals the consumers right. 05:41.810 --> 05:45.590 And while implementing the solution, please use the following guideline. 05:45.590 --> 05:49.970 Use as many printers as possible so that you can debug the program easily. 05:49.970 --> 05:56.390 The program, which involves multithreading are hard to debug using debugging tools such as GDB or et 05:56.390 --> 05:57.110 cetera. 05:57.350 --> 06:03.860 Print f should be extensively used in your program so that if your program encounter a deadlock like 06:03.860 --> 06:10.700 situation, you can very well analyze the logs or the sequence of events taking place from the print 06:10.700 --> 06:11.420 f output. 06:11.420 --> 06:15.170 And you would figure it out that what exactly the problem is. 06:15.170 --> 06:15.890 Right? 06:16.250 --> 06:21.830 And going further, since in our program we need to make use of the data structure. 06:21.830 --> 06:29.300 So Q dot is the header file and this header file will give you the access to the following APIs, right? 06:29.330 --> 06:36.020 You can see on the right hand side that you can make use of the Q by using the following APIs in this 06:36.020 --> 06:36.530 way. 06:36.530 --> 06:42.900 So this is the example usage regarding how you can make use of the Q in your program. 06:42.900 --> 06:49.260 So for example, if you want to create a new Q, you can simply use the API init Q and it will give 06:49.260 --> 06:52.350 you a pointer to the Q which has been initialized. 06:52.440 --> 06:59.240 Similarly, if you need to check whether the Q is empty, you can use this API and in order to enqueue 06:59.250 --> 07:04.380 an integer element into the Q, you can simply use the Q API, right? 07:04.380 --> 07:09.120 So in this example we are simply queuing up the element five in the queue. 07:09.300 --> 07:13.200 And in case if you remove an element from the queue, you can use an API. 07:13.410 --> 07:19.050 Q Right, it will remove an element from the queue and it will give you an integer value. 07:20.440 --> 07:25.870 Similarly, if you need to find how many elements are present in the queue, you can use this queue 07:25.930 --> 07:27.160 underscore count. 07:27.190 --> 07:28.000 Right. 07:28.120 --> 07:34.420 And this is another is queue full which will tell you whether your queue is full or not. 07:34.450 --> 07:39.820 So while writing the solution which implements producer consumer problem statement that we have just 07:39.820 --> 07:45.580 discussed, you need to make use of these APIs on the queue data structure, right? 07:46.120 --> 07:52.690 So now in the next lecture video, let us set up our homework problem to begin with and then we will 07:52.690 --> 07:58.420 discuss how to write producer and consumer algorithms in order to implement the producer consumer problem 07:58.420 --> 08:04.180 statement that we have discussed and also respect all the constraints that we have discussed.