WEBVTT 00:05.210 --> 00:06.830 So welcome back, guys. 00:06.860 --> 00:12.050 Now, in this section of the course, we will get ourselves familiar with some technical words which 00:12.050 --> 00:13.940 is related to Multi-threading world. 00:15.590 --> 00:18.410 So this section will be a little bit theoretical. 00:18.410 --> 00:24.290 We will going to understand the exact meaning of these words, that is context switching, concurrency 00:24.290 --> 00:25.430 and parallelism. 00:25.430 --> 00:30.920 Because when we will be doing assignments and projects on Multi-threading, then in order to explain 00:30.920 --> 00:34.820 the Multithreading concepts, I would be using these terms too often. 00:35.030 --> 00:38.860 So let us try to understand the meaning of these words in this section. 00:38.870 --> 00:43.160 So to start with, let us understand what exactly concurrency means. 00:43.280 --> 00:50.270 So concurrency simply means that doing two or more different tasks, but the pattern in which you are 00:50.270 --> 00:55.010 doing these tasks determines whether it is a concurrency or not. 00:55.160 --> 01:04.690 So if you do two or more tasks such that you do only one task at a time and you switch between the task. 01:04.700 --> 01:09.240 Now there is a condition that is imposed while you switch between these tasks. 01:09.450 --> 01:15.000 If you switch between the task by preempting the current task that you are doing, then picking up the 01:15.000 --> 01:18.750 next task partially do it and then preempt it again. 01:18.900 --> 01:23.730 Then again picking up the next task, partially do it and then preempt it again. 01:23.730 --> 01:27.090 And you continue to follow the same pattern, right? 01:27.090 --> 01:32.730 And eventually you will end up picking up the first task from the same point where it was left. 01:32.760 --> 01:37.020 Then again, you partially do it and again you preempt it, right? 01:37.020 --> 01:42.660 So you will continue to perform each task in a round robin fashion, preempting the one task, picking 01:42.660 --> 01:44.310 up the next, and so on. 01:45.700 --> 01:52.200 So if you perform two or more tasks in this fashion, then this shows the property of concurrency, 01:52.210 --> 01:52.930 right? 01:54.440 --> 01:59.120 Let us take one real world example which shows the property of concurrency. 01:59.900 --> 02:05.870 So let us suppose that there are three well-diggers that is three persons which has the responsibility 02:05.870 --> 02:11.870 to dig the well, and they are assigned a task to dig their respective 100ft deep. 02:11.870 --> 02:12.440 Well. 02:12.470 --> 02:13.190 Right. 02:13.190 --> 02:18.950 So if there are three well diggers, then each of the well digger has to dig 100ft deep. 02:18.950 --> 02:20.180 Well, right. 02:20.180 --> 02:27.710 So it means that there are three wells to be digged and there is a condition that all three well diggers 02:27.710 --> 02:30.860 have only one well drilling tool. 02:30.860 --> 02:31.520 Right. 02:31.520 --> 02:33.230 Which they have to share. 02:33.380 --> 02:34.180 Right. 02:34.190 --> 02:35.600 So now let us see that. 02:35.600 --> 02:42.710 In what pattern should they dig the well so that the property of concurrency is honored. 02:42.980 --> 02:48.980 So the conditions or constraints that need to be imposed on three well, Digger is that that only one 02:48.980 --> 02:51.050 person can dig a well at a time. 02:51.050 --> 02:57.320 And this is quite obvious because in this example there is only one drilling tool available, right? 02:57.320 --> 03:01.740 So it is quite obvious that only one person can dig a well at a time. 03:02.040 --> 03:09.570 And when current person who is digging the well take rest because he got tired, then the current person 03:09.570 --> 03:15.000 hand over the digging tool to the second person and second person resumed digging his well from the 03:15.000 --> 03:17.250 same point where he left last time. 03:17.430 --> 03:23.250 Similarly, when second person got tired and he wants to take rest, he hand over the digging tool to 03:23.250 --> 03:26.340 the third person and third person resumes again. 03:26.340 --> 03:27.150 Right. 03:27.150 --> 03:33.420 And this process continues until all the three well-diggers complete their respective tasks. 03:33.450 --> 03:38.820 That is all the three well diggers successfully dig their respective 100ft deep. 03:38.820 --> 03:40.170 Well, right. 03:40.380 --> 03:45.350 So you can see that this real world example shows the property of concurrency. 03:45.360 --> 03:51.600 We can conclude that work of all the three well diggers was in progression, right? 03:51.630 --> 03:57.420 Though they were slow because they had to share the same well drilling tool between them. 03:57.420 --> 04:03.240 But at least we can say that the work of all the three well diggers was in progression. 04:03.330 --> 04:04.710 It was not like that. 04:04.710 --> 04:05.190 That one. 04:05.190 --> 04:10.590 Well, Digger had not even started and the rest two were digging the well one by one. 04:10.590 --> 04:11.310 Right. 04:11.850 --> 04:13.890 At any given point of time. 04:13.890 --> 04:19.860 There was some percentage of work completed by each of the three Well-diggers Right. 04:20.040 --> 04:25.710 So two or more tasks which is done in this fashion are concurrent in nature, right? 04:26.010 --> 04:32.610 Later, we will try to map this real world example to the world of Multithreading and see that exact 04:32.610 --> 04:36.300 same pattern is followed by multiple concurrent threads.