1 00:00:00,330 --> 00:00:04,170 Okay, guys this is Mail Bag week number two we have a bunch of things for you 2 00:00:04,170 --> 00:00:08,190 you'll see not only the Mail Bag, but you will see a couple of new lectures that 3 00:00:08,190 --> 00:00:12,270 are, are intended to ease some of the pain when you are moving from assignments 4 00:00:12,270 --> 00:00:16,050 to assignments so essentially we're going to update you on the, on your 5 00:00:16,050 --> 00:00:23,989 progress in aggregate terms, okay? And then we'll go into some of the more 6 00:00:23,989 --> 00:00:27,883 specific topics, some of the questions that you guys ask, and, and give you, you 7 00:00:27,883 --> 00:00:31,718 know, more hints on which video to look next if you have some different kinds of 8 00:00:31,718 --> 00:00:37,440 issues, okay? So this is the number of students active. 9 00:00:37,440 --> 00:00:40,875 We have about 11,000 students active right now, this week. 10 00:00:40,875 --> 00:00:44,710 You know it was 17 last week its a you know a normal decrease at this point not 11 00:00:44,710 --> 00:00:48,545 worry about that, this is also something that is interesting to report this is 12 00:00:48,545 --> 00:00:52,852 essentially the, the prolonging languages that people are reported to know during 13 00:00:52,852 --> 00:01:00,430 one of the survey its very interesting to see how popular Python has become, okay? 14 00:01:00,430 --> 00:01:03,220 And obviously a lot of you are using Python as the implementation language 15 00:01:03,220 --> 00:01:06,360 here. so this is an interesting statistics. 16 00:01:06,360 --> 00:01:10,114 it was kind of surprising to me. Especially the number of people who know 17 00:01:10,114 --> 00:01:15,704 MATLAB compared to other languages. video views 11,000 this week of the 18 00:01:15,704 --> 00:01:20,020 introductory video, okay? So this is pretty good. 19 00:01:20,020 --> 00:01:23,481 The, you see the numbers here? For CP, local search you know 20 00:01:23,481 --> 00:01:27,610 mathematical programming. Very healthy, it's normal. 21 00:01:27,610 --> 00:01:30,340 You know, we are still looking, we are still at the beginning of the class. 22 00:01:30,340 --> 00:01:32,710 We are not expecting people to look at these right now. 23 00:01:32,710 --> 00:01:36,810 you know, the assignments are also prgoressing in each of these topics. 24 00:01:36,810 --> 00:01:40,308 4,000 views of the mail back last week. This is good you know, a little, you 25 00:01:40,308 --> 00:01:43,100 know, people could, you know, actively look at this. 26 00:01:43,100 --> 00:01:46,691 because this is giving also a lot of hints on how to actually approach the 27 00:01:46,691 --> 00:01:49,380 classes. And answering kind of questions globally 28 00:01:49,380 --> 00:01:52,827 as well. this is the students active in the class, 29 00:01:52,827 --> 00:01:55,140 okay? in in assignments. 30 00:01:55,140 --> 00:01:57,680 And once again, you know, you have a drop, okay? 31 00:01:57,680 --> 00:02:00,635 which is roughly the number, the same drop as active students [INAUDIBLE]. 32 00:02:00,635 --> 00:02:04,851 Okay what you see here is interesting, So, the number of submission which have 33 00:02:04,851 --> 00:02:08,447 been graded has a very tiny drop, [INAUDIBLE], I mean, it's a drop, but 34 00:02:08,447 --> 00:02:14,438 it's not huge, okay, which is also good. People are, you know, basically, moving 35 00:02:14,438 --> 00:02:17,600 along to the next assignments, which is very nice. 36 00:02:17,600 --> 00:02:20,548 And this is the number of submission by active students you see that actually the 37 00:02:20,548 --> 00:02:23,364 students who are active are actually submitting more which is, which is also 38 00:02:23,364 --> 00:02:27,049 great, okay. So I'll give you some more graph in a 39 00:02:27,049 --> 00:02:30,770 moment, but this is the big picture at this point, okay this is also the 40 00:02:30,770 --> 00:02:35,162 participation we've assignment what you see is two column the, the maximum number 41 00:02:35,162 --> 00:02:41,755 of submission for a [UNKNOWN] plotting a problem and the minimum ones. 42 00:02:41,755 --> 00:02:45,598 you see that knapsack is about you know the, the least you know 2, you know 43 00:02:45,598 --> 00:02:50,234 2.5000 students submitting are submitting the various the, the various solutions 44 00:02:50,234 --> 00:02:54,321 the maximum is 3, 3000 which is good, okay, so very healthy also are the number 45 00:02:54,321 --> 00:02:58,347 for you know colouring its about close to a 1000 if you could raised that a little 46 00:02:58,347 --> 00:03:05,633 bit that would be terrific. And you see that some people have 47 00:03:05,633 --> 00:03:09,720 actually already, you know solved all the assignments and some of the puzzle 48 00:03:09,720 --> 00:03:14,158 challenge as well, okay? But once again, we don't expect that, you 49 00:03:14,158 --> 00:03:16,890 know. This is a week by week class, okay? 50 00:03:16,890 --> 00:03:19,830 We give you all, you know, you can do everything you want but we, we assume 51 00:03:19,830 --> 00:03:23,113 that people are going to progress week by week on every one of these assignments, 52 00:03:23,113 --> 00:03:28,135 okay? no for the grading, once again i want to 53 00:03:28,135 --> 00:03:32,935 set the expectation right,so, so getting all 10's in this class is amazingly 54 00:03:32,935 --> 00:03:38,100 difficult. Ok so, so we are not expecting you know? 55 00:03:38,100 --> 00:03:43,280 a large number of students to actually achieve that This is not their intent. 56 00:03:43,280 --> 00:03:45,900 That would be really really terrific, okay? 57 00:03:45,900 --> 00:03:49,260 But this is, this requires a lot of work. This requires a lot of knowledge. 58 00:03:49,260 --> 00:03:51,608 And even that. That requires a lot of time just getting 59 00:03:51,608 --> 00:03:55,860 these solutions on every one of them. So we don't expect you to do that, in a 60 00:03:55,860 --> 00:03:58,485 sense. So what we want the class to do is focus 61 00:03:58,485 --> 00:04:01,110 on the seven first. You know, solve the assignments. 62 00:04:01,110 --> 00:04:02,990 Get seven on everything. You get a. 63 00:04:02,990 --> 00:04:06,400 Certification at the end and that is really feasible, you know, as far as we 64 00:04:06,400 --> 00:04:10,470 can judge, okay? So the bar is set reasonably for getting 65 00:04:10,470 --> 00:04:14,664 7's on all of the parts.OK? Now what you can do is once you get these 66 00:04:14,664 --> 00:04:17,628 7's, once you have allegories, well several allegories for popular 67 00:04:17,628 --> 00:04:22,370 assignments, and you get 7 on them, you can say oh no I want to proof. 68 00:04:22,370 --> 00:04:26,010 That's good, that's healthy and this is what we want you to do. 69 00:04:26,010 --> 00:04:29,580 But don't focus on 1 particular thing, and say, oh I don't get a 10 on that one. 70 00:04:29,580 --> 00:04:32,740 Okay, so learn more techniques inside during the class. 71 00:04:32,740 --> 00:04:35,820 And you can always go back to these assignments, and correct them. 72 00:04:35,820 --> 00:04:39,025 We lea, we give you some weeks at the end to actually do that. 73 00:04:39,025 --> 00:04:42,301 Okay, so in a sense, guarantee you're doing craft coloring and let's say you 74 00:04:42,301 --> 00:04:45,473 haven't look at the local set lecture, you can go, you know, let's say five 75 00:04:45,473 --> 00:04:48,697 times all of the six party [UNKNOWN] but the last one you can't, you will see 76 00:04:48,697 --> 00:04:55,020 techniques later on, you can go back there and maybe get a 10 on that one. 77 00:04:55,020 --> 00:04:58,510 Okay, that is the essence of the class, right? 78 00:04:58,510 --> 00:05:02,530 So so you don't have to focus on getting every ten, every you know, a ten on every 79 00:05:02,530 --> 00:05:08,630 part of the assignment before moving to the next assignment, don't do that okay. 80 00:05:08,630 --> 00:05:11,894 so there are basically two approaches here that you can always do when you want 81 00:05:11,894 --> 00:05:14,966 to improve right, so you can have the scaleable solution right that I was just 82 00:05:14,966 --> 00:05:17,942 talking about, trying to get seven everywhere Okay, and when you get that, 83 00:05:17,942 --> 00:05:20,870 you basically get, you know, this is basically trying to find an approach 84 00:05:20,870 --> 00:05:27,470 which scales, well on all the parts essentially, on all the instances. 85 00:05:27,470 --> 00:05:29,927 If you can get that, it's not going to be the best algorithm, but you get a good 86 00:05:29,927 --> 00:05:32,886 grade, right. So, you get, you know, essentially 7, on 87 00:05:32,886 --> 00:05:36,320 the 6 part you get 42 for every one assignment. 88 00:05:36,320 --> 00:05:38,986 The other way to do it is to say ooh, I really want some of these 10's, I want to 89 00:05:38,986 --> 00:05:42,850 prove [UNKNOWN] on these problems and it's possible, right. 90 00:05:42,850 --> 00:05:46,946 And when you do that, you may say, oh but that approach doesn't scale as well as 91 00:05:46,946 --> 00:05:52,360 let's say, another approach, okay? But that's fine as well. 92 00:05:52,360 --> 00:05:56,720 You could say, okay, so on four of these [UNKNOWN] I get a ten, on the last two... 93 00:05:56,720 --> 00:06:00,437 I get a 3 because its not scaring you get a still 4 or 6 which is a very nice grade 94 00:06:00,437 --> 00:06:04,154 right, and then later on in the class you can say oh but i have a little bit more 95 00:06:04,154 --> 00:06:08,048 time ,this is the last two weeks, i could see if i can implement something else to 96 00:06:08,048 --> 00:06:11,942 raise that bar, so that's also something you can do,so these two approaches are 97 00:06:11,942 --> 00:06:15,541 what we want you guys to do and we will say how you can get there in some of the 98 00:06:15,541 --> 00:06:24,426 new video that i am going to you know mention in moment. 99 00:06:24,426 --> 00:06:27,778 Once again getting 10 on everything is really hard, okay? 100 00:06:27,778 --> 00:06:31,084 that's why we have a specific distinctions for that particular, for 101 00:06:31,084 --> 00:06:34,854 those people who could actually do that ,so in the sense don't focus on getting 102 00:06:34,854 --> 00:06:39,164 10 in everything. Okay, so its just very very hard and 103 00:06:39,164 --> 00:06:42,934 graphically in particular in very very hard So, this is a curve which is really 104 00:06:42,934 --> 00:06:46,414 interesting. What you see, so this, this is 105 00:06:46,414 --> 00:06:50,166 essentially you know seven of the, the red line that you see there is getting a 106 00:06:50,166 --> 00:06:53,638 seven of average on all the parts that you are assuming to have completed by 107 00:06:53,638 --> 00:06:58,298 now, okay? So, what you see is that there are about 108 00:06:58,298 --> 00:07:02,170 800 students, you know You know, on the right of this curve so 109 00:07:02,170 --> 00:07:05,348 those people are on track. What you see also is a large body of 110 00:07:05,348 --> 00:07:08,612 students that are very, very close and our goal is to take these guys and bring 111 00:07:08,612 --> 00:07:13,074 them over the curve, okay? And so, those people who are there they 112 00:07:13,074 --> 00:07:16,665 just don't have to worry so look at the stuff that we are saying today, look at 113 00:07:16,665 --> 00:07:20,028 the stuff that we present in the lectures, and that should allure you to 114 00:07:20,028 --> 00:07:25,375 go over this bar, okay? Sending expectation right, don't get to, 115 00:07:25,375 --> 00:07:27,990 don't try to get that. Okay, so the goal is to have a seven or 116 00:07:27,990 --> 00:07:30,184 average. Okay, you don't have to be the best in 117 00:07:30,184 --> 00:07:32,604 everything. Okay, so you will have more time later on 118 00:07:32,604 --> 00:07:36,100 to actually refine those assignment and that's the goal here right. 119 00:07:36,100 --> 00:07:39,182 So, we want to bring you over this curve, and you will some of the techniques that, 120 00:07:39,182 --> 00:07:41,712 some of the strategies that we are following to actually do that in 121 00:07:41,712 --> 00:07:45,050 practice, okay? So, we want these people to move, you 122 00:07:45,050 --> 00:07:47,444 know, across this curve and that's the goal, that's the goal of the couple of 123 00:07:47,444 --> 00:07:51,476 lectures that we are going to present. Okay, now there are a lot of questions 124 00:07:51,476 --> 00:07:54,485 that, you know, lot of questions on the board and people are very good at 125 00:07:54,485 --> 00:07:57,902 responding to them.They are three of them that always, you know, come back Okay, 126 00:07:57,902 --> 00:08:02,314 and we want to address them. The first one is why is this class so 127 00:08:02,314 --> 00:08:04,510 hard, then you know, I am completely lost, how do I get started, and we love 128 00:08:04,510 --> 00:08:07,392 the [UNKNOWN] as well. Okay, and what is really the goal of this 129 00:08:07,392 --> 00:08:09,813 class, okay? Okay, and what is really the goal of this 130 00:08:09,813 --> 00:08:12,388 class, okay? And so I think, you know, we basically 131 00:08:12,388 --> 00:08:16,420 specify those things at the beginning but I want to go over again. 132 00:08:16,420 --> 00:08:19,285 Over them again, okay? So, why is this class so hard? 133 00:08:19,285 --> 00:08:23,340 It's the basic principle that we have, this is the way we want to teach. 134 00:08:23,340 --> 00:08:27,410 So there is this beautiful, you know, Beatles song, I want to hold your hand. 135 00:08:27,410 --> 00:08:29,650 That's not what we are about, we don't want to do that. 136 00:08:29,650 --> 00:08:32,423 We don't want to give you the algorithm for graph coloring, and tell you, 137 00:08:32,423 --> 00:08:35,655 implement it, okay? So, because you don't learn as much as 138 00:08:35,655 --> 00:08:39,686 saying this other principle, okay? You can apply them to all these problems, 139 00:08:39,686 --> 00:08:42,013 okay? But now, you have to find the one that's, 140 00:08:42,013 --> 00:08:44,620 that is right for this particular problem. 141 00:08:44,620 --> 00:08:46,930 And you have to actually [INAUDIBLE] it yourself, so that. 142 00:08:46,930 --> 00:08:50,590 you can actually understand, or you put this [UNKNOWN] in practice, okay? 143 00:08:50,590 --> 00:08:54,010 And so, for me, you know the best way to do that, is actually get your hands 144 00:08:54,010 --> 00:08:57,214 dirty. Don't get to many guidelines, because 145 00:08:57,214 --> 00:09:01,540 when you discover things yourself, there are two things that happens. 146 00:09:01,540 --> 00:09:03,490 First you are going to retain them much better. 147 00:09:03,490 --> 00:09:06,410 And the second thing, is it's going to boost your confidence. 148 00:09:06,410 --> 00:09:09,301 And you know that if you see a problem later on Oh, I have done it for graph 149 00:09:09,301 --> 00:09:11,860 coloring. I know I can do it for, let's say, time 150 00:09:11,860 --> 00:09:13,060 tabling. Okay? 151 00:09:13,060 --> 00:09:15,360 So, in a sense, what we want is these two things. 152 00:09:15,360 --> 00:09:17,660 We want you to retain doing formation bets better. 153 00:09:17,660 --> 00:09:21,000 And by doing it yourself, you will retain that better, okay? 154 00:09:21,000 --> 00:09:23,370 And then the second thing that we want, okay? 155 00:09:23,370 --> 00:09:32,246 Is that you are also able to, to. in a sense, apply this much more widely 156 00:09:32,246 --> 00:09:35,698 later on, okay? And to do that, you have to have the 157 00:09:35,698 --> 00:09:39,289 confidence that you know that if, you havn't seen that problem, I have not to 158 00:09:39,289 --> 00:09:43,500 much guidance and I can apply it. Now I want to tell you a story. 159 00:09:43,500 --> 00:09:47,269 So I got educated in Europe. Most of my studies were memorizing 160 00:09:47,269 --> 00:09:50,057 things. And there were 2 or 3 classes that were 161 00:09:50,057 --> 00:09:52,980 not like that, and one of them was just crazy, right? 162 00:09:52,980 --> 00:09:56,457 So we were graded on 20 and that class, all the students had above 16, okay, 163 00:09:56,457 --> 00:10:00,162 well, part of the students had about 16 and part of the students below 4, you can 164 00:10:00,162 --> 00:10:04,881 imagine, right? And it was like, more like 20%, 80%, so 165 00:10:04,881 --> 00:10:08,474 it was crazy, right? So this is the first time the professor 166 00:10:08,474 --> 00:10:12,687 was actually giving that class, okay? he was not able to actually give that 167 00:10:12,687 --> 00:10:16,586 kind of grade later on, he got, you know. Told that, you know, this is not the way 168 00:10:16,586 --> 00:10:18,900 you should grade. But anyway, so with that class, what's 169 00:10:18,900 --> 00:10:21,290 really, really transformally for me, alright? 170 00:10:21,290 --> 00:10:25,110 So it's just the only thing that that class was trying to tell you is that. 171 00:10:25,110 --> 00:10:27,650 You know, use your mind, try to solve the problem, okay? 172 00:10:27,650 --> 00:10:31,090 So we try to do that, but a much weaker extent in a sense, right? 173 00:10:31,090 --> 00:10:33,910 So here we are giving you a lot of guidance. 174 00:10:33,910 --> 00:10:37,738 But not sufficiently so that we give you, you know, an [UNKNOWN] that you have to 175 00:10:37,738 --> 00:10:40,265 quote. So, this is the spirit of this class 176 00:10:40,265 --> 00:10:42,430 Okay. So, the second thing that we want to do 177 00:10:42,430 --> 00:10:45,310 is for you to experience NP-hardness Okay, so we are not cheating any 178 00:10:45,310 --> 00:10:49,236 [UNKNOWN] Okay. So, when we give you graph coloring this 179 00:10:49,236 --> 00:10:53,810 is an amazingly hard problem Okay. So, we did it on purpose right. 180 00:10:53,810 --> 00:10:57,361 So, graph coloring is where you say these problem are really, really, really 181 00:10:57,361 --> 00:11:02,380 difficult, I can't prove up optimality on you know, the largest instance, okay? 182 00:11:02,380 --> 00:11:05,220 And this is on purpose. We want to show you that this is really 183 00:11:05,220 --> 00:11:08,170 really hot, okay? And the only way we can show you that is 184 00:11:08,170 --> 00:11:10,710 by you experiencing it, okay? You try it. 185 00:11:10,710 --> 00:11:13,190 If I tell you why would you believe me, okay? 186 00:11:13,190 --> 00:11:15,950 And in the sense if I only give you instance which are turkey notes, okay, 187 00:11:15,950 --> 00:11:19,610 you can solve them optimally and then it's not even fact, okay? 188 00:11:19,610 --> 00:11:23,282 So, here we want you to really experience you know these are really hard problems, 189 00:11:23,282 --> 00:11:26,347 okay? And problems in practice are, you know, 190 00:11:26,347 --> 00:11:29,532 rough coloring, you know, is very hard but problems in practice are often that 191 00:11:29,532 --> 00:11:32,249 hard. Okay, and You have to be really clever in 192 00:11:32,249 --> 00:11:35,400 how you actually approach them. So, in a sense we want you to really 193 00:11:35,400 --> 00:11:38,891 experience this thing. Okay, there is something called, you 194 00:11:38,891 --> 00:11:42,060 know, NP, NP-hardness. And this is tough okay. 195 00:11:42,060 --> 00:11:45,900 And so that was the goal of the, of the, the graph coloring assignment, okay. 196 00:11:45,900 --> 00:11:48,540 And once again, as I told you, we want you to be able to apply these ideas to 197 00:11:48,540 --> 00:11:52,036 another problem, okay. And so in a sense what we do, we covered, 198 00:11:52,036 --> 00:11:56,200 you know, the paradigms but we don't cover the real implementation. 199 00:11:56,200 --> 00:11:59,000 That's for you to discover, that's the basic principal of this class. 200 00:11:59,000 --> 00:12:02,417 And then we cover modeling techniques, but you will have to creative in choosing 201 00:12:02,417 --> 00:12:07,060 the one you apply for popular [UNKNOWN]. So that's the basic idea. 202 00:12:07,060 --> 00:12:10,130 And that's why its so hard, you have to discover a lot of things yourself. 203 00:12:10,130 --> 00:12:13,760 We don't take your hand, okay, now, so we understand that, you know, you know 204 00:12:13,760 --> 00:12:17,555 sometimes it's really, it's really, you know, it's really hard for different, for 205 00:12:17,555 --> 00:12:20,910 different people in the class or we understand that the diversity here is 206 00:12:20,910 --> 00:12:24,375 very large compared to some of the classrooms in which we have been teaching 207 00:12:24,375 --> 00:12:30,386 similar classes. And so, what we going to do is to, to 208 00:12:30,386 --> 00:12:34,250 actually try to help you or help some of you actually in, in covering a little bit 209 00:12:34,250 --> 00:12:37,498 in more detail some, some of the techniques that you know we basically 210 00:12:37,498 --> 00:12:40,858 assume people would know, okay and so we have three new lectures that I am 211 00:12:40,858 --> 00:12:44,498 going to talk about and please watch them if you are just you know on the, on the 212 00:12:44,498 --> 00:12:51,100 on the left of this curve. On the right of this curve? 213 00:12:51,100 --> 00:12:52,934 Well, whatever. You know, on the wrong side of that curve 214 00:12:52,934 --> 00:12:55,640 and we want to bring you along on the left side of the curve. 215 00:12:55,640 --> 00:12:59,030 Okay, so look at this because they're going to help you, okay? 216 00:12:59,030 --> 00:13:02,750 So we have two, two, two new techniques which are greedy, you know, one and two. 217 00:13:02,750 --> 00:13:05,800 That's basically telling you this is where you should start from, okay? 218 00:13:05,800 --> 00:13:09,118 So start from a greedy algorithm. And that will help you understand the 219 00:13:09,118 --> 00:13:12,238 nature of the problem and will give you some guidance on this okay, and then, you 220 00:13:12,238 --> 00:13:15,070 know what we want to talk a little bit about you know, if you, if you want to 221 00:13:15,070 --> 00:13:18,142 start on this assignment, this is a plan okay this is really you know, if you are 222 00:13:18,142 --> 00:13:20,974 you know not sure on how to approach them, you know, use this strategy okay 223 00:13:20,974 --> 00:13:27,980 and so that's the two you know three lectures I'm going to cover. 224 00:13:27,980 --> 00:13:31,498 in a moment, okay? Now, learning goals of the class is, is 225 00:13:31,498 --> 00:13:34,683 the class you know trying to teach you to use a solver or to learn how to build 226 00:13:34,683 --> 00:13:38,696 one. It's, it's, it's neither of them but it 227 00:13:38,696 --> 00:13:41,816 gives you insight how to, how to do this but the real, the real message from this 228 00:13:41,816 --> 00:13:44,984 class is that if you have an optimization problem, so, these are some of the most 229 00:13:44,984 --> 00:13:51,150 successful methodologies to solve them and we want you to understand that. 230 00:13:51,150 --> 00:13:53,430 And we want you to understand them so that you can actually code these 231 00:13:53,430 --> 00:13:56,348 algorithms yourself, okay? So you have enough information 232 00:13:56,348 --> 00:13:59,910 afterwards, you have enough informtaion to trnaslate that into code. 233 00:13:59,910 --> 00:14:02,870 Of course it's hard, but you have the information to do it, okay? 234 00:14:02,870 --> 00:14:05,060 And you can always use the forum and discuss with other people. 235 00:14:05,060 --> 00:14:08,570 The collaboration policy here is very lenient, okay? 236 00:14:08,570 --> 00:14:11,644 And then but, but that's the essence you could say oh I want to implement 237 00:14:11,644 --> 00:14:15,248 something in constraint programming and I really now how to do it, okay and now you 238 00:14:15,248 --> 00:14:18,640 implemented and then discovery oh, that what it takes and so on, that's one of 239 00:14:18,640 --> 00:14:21,873 the big goals of the, of the, of the class now it also give you the ability to 240 00:14:21,873 --> 00:14:25,371 use solvers you know in, in appropriately so we'll talk about that in, in some of 241 00:14:25,371 --> 00:14:28,604 the when, when we talk about the way to approach the assignments, okay But 242 00:14:28,604 --> 00:14:31,837 essentially a solver is only as good as your understanding of the various 243 00:14:31,837 --> 00:14:40,238 methodologies, okay? So you can put things in a solver and 244 00:14:40,238 --> 00:14:44,900 they can, the solvers can run forever if you're not mothering the problem right. 245 00:14:44,900 --> 00:14:47,086 Okay? And so in a sense, you know, we, we, you 246 00:14:47,086 --> 00:14:50,838 have to understand really how the various techniques are working so that you can 247 00:14:50,838 --> 00:14:54,366 use these solvers in an appropriate fashion.In a sense think about it here, 248 00:14:54,366 --> 00:14:57,950 you know when you look at solver we give the principles you can see through the 249 00:14:57,950 --> 00:15:01,534 layers and decide if that's going to be a good solver for your problem or not, how 250 00:15:01,534 --> 00:15:05,174 you should model your problem and so on Okay, so we'll come back to that because 251 00:15:05,174 --> 00:15:08,478 you know, some of the solvers you can take off the shelf and try to apply to 252 00:15:08,478 --> 00:15:11,726 the problems in this class won't be enough to get you a ten okay, so I'll 253 00:15:11,726 --> 00:15:21,718 come back to that later on okay. But it give you the ability to use a 254 00:15:21,718 --> 00:15:24,662 solver and then you can extend the solver so you can you know tailor them so that 255 00:15:24,662 --> 00:15:28,002 they work for your particular problem, okay. 256 00:15:28,002 --> 00:15:31,122 So, also implementing a solver is a completely different ball games but, once 257 00:15:31,122 --> 00:15:34,242 again you will have the principles and the knowledge to actually go deeper and 258 00:15:34,242 --> 00:15:37,170 look at the right paper see if you want to ever want implement a solver like 259 00:15:37,170 --> 00:15:41,234 this, okay? So, we give you the tools for doing a lot 260 00:15:41,234 --> 00:15:44,472 of different things. But the core here is understanding the 261 00:15:44,472 --> 00:15:48,000 methodologies at a level where you will you know, be able to go deeper in many 262 00:15:48,000 --> 00:15:51,920 different areas of optimization, whether it is application, whether it is solver, 263 00:15:51,920 --> 00:15:57,376 whether it is more, you know, sophisticated algorithm, okay? 264 00:15:57,376 --> 00:16:00,294 yes. Okay, so this is important, okay, I want 265 00:16:00,294 --> 00:16:03,697 to cover this. So if you use a solver, so, so some 266 00:16:03,697 --> 00:16:07,784 people may say, ooh, but the guys who actually know solver have a complete 267 00:16:07,784 --> 00:16:11,230 advantage on this class. Okay? 268 00:16:11,230 --> 00:16:13,309 So first, I don't think it's true. Okay? 269 00:16:13,309 --> 00:16:15,920 Because if you code, you could, you can do two things in this class. 270 00:16:15,920 --> 00:16:19,540 You can code the algorithm yourself. And you can actually get a certificate. 271 00:16:19,540 --> 00:16:22,378 It's going to take you a little bit, you know, longer than somebody who knows the 272 00:16:22,378 --> 00:16:23,600 solver. Okay? 273 00:16:23,600 --> 00:16:26,912 But you will learn a lot, okay? So you learn more than just, you know, 274 00:16:26,912 --> 00:16:29,890 learning a solver and then using it in a naive fashion, okay? 275 00:16:29,890 --> 00:16:33,124 So in a sense, yes, these people will get a, you know, let's say get a certificate 276 00:16:33,124 --> 00:16:36,529 in an easier fashion. You can do it without knowing these 277 00:16:36,529 --> 00:16:39,320 solvers, okay? But the really important point is that if 278 00:16:39,320 --> 00:16:42,620 you look at the way the assignments are chosen, okay, they have been chosen such 279 00:16:42,620 --> 00:16:45,720 that If you taken off the shelf solver use it in a naive fashion, okay or even 280 00:16:45,720 --> 00:16:48,970 in a sophisticated fashion is going to be really difficult for you to get 10 on all 281 00:16:48,970 --> 00:16:54,290 the assignments, okay. If you know one solver try to apply it to 282 00:16:54,290 --> 00:16:56,550 all the assignments its going to be tough, okay? 283 00:16:56,550 --> 00:17:00,149 Okay so in a sense what I am telling you here is that if you want to [UNKNOWN] 284 00:17:00,149 --> 00:17:04,043 many of these assignments You'll have to really creative and go beyond you know 285 00:17:04,043 --> 00:17:09,550 this, you know just a naive or a simple use of the solvers. 286 00:17:09,550 --> 00:17:12,550 You need to combine you use them in a clever fashion or you will need to use 287 00:17:12,550 --> 00:17:17,480 sophisticated technique on top of them or inside them and things like this, okay? 288 00:17:17,480 --> 00:17:20,693 So once again you know, yeah the reason advantage is viewing a solver but its 289 00:17:20,693 --> 00:17:23,466 minimum. Okay, and if you want to get ten on some 290 00:17:23,466 --> 00:17:26,308 of these assignments you have to go beyond what the solver do or use the 291 00:17:26,308 --> 00:17:31,135 solver really creatively Okay? So, so, so this is just to give you that 292 00:17:31,135 --> 00:17:34,328 in perspective. There is not that much of an advantage to 293 00:17:34,328 --> 00:17:37,293 use a solver. It becomes more an advantage on the 294 00:17:37,293 --> 00:17:42,210 final, on the final assignments, but even in those cases, okay? 295 00:17:42,210 --> 00:17:44,938 What you have to understand is that you will have to use this solver in a very 296 00:17:44,938 --> 00:17:47,723 clever fashion. It's just not knowing the solver that's 297 00:17:47,723 --> 00:17:50,500 going to help you, you have to know the material as well, okay? 298 00:17:50,500 --> 00:17:53,070 So, what next. coloring was hard. 299 00:17:53,070 --> 00:17:55,926 It was intended to do that. You have experience in p-hardness. 300 00:17:55,926 --> 00:18:01,646 With with with, with this, okay? So, it's, it's, it's, it's a very 301 00:18:01,646 --> 00:18:04,862 interesting problem because it's very easy to state, and it's incredibly hard, 302 00:18:04,862 --> 00:18:07,372 OK? And this is why this assignment is 303 00:18:07,372 --> 00:18:10,840 positioned there, OK? But it's, it's essentially a shock and 304 00:18:10,840 --> 00:18:13,170 it's, it was intended to be a shock, right? 305 00:18:13,170 --> 00:18:15,360 So the traveling salesman problem is going to be very different. 306 00:18:15,360 --> 00:18:18,132 Finding feasible solution is going to be really easy, but there are many, many 307 00:18:18,132 --> 00:18:21,315 different tools, okay? And here is going to be whole world can 308 00:18:21,315 --> 00:18:24,096 you optimize. Okay, it's the, as, as I said in the 309 00:18:24,096 --> 00:18:29,080 lectures, it's the most, you know, well known optimization problem, okay. 310 00:18:29,080 --> 00:18:33,289 and, once again, you know, I think you should focus on getting it, getting seven 311 00:18:33,289 --> 00:18:38,880 first, and then trying to see if you can turn them into a ten, okay. 312 00:18:38,880 --> 00:18:41,274 It's really tough to get, you know, optimal solution of some of these 313 00:18:41,274 --> 00:18:44,350 benchmarks as well. It's doable, but it's very tough, so, you 314 00:18:44,350 --> 00:18:47,400 know You know, be reasonable in the standards that you have and then try to 315 00:18:47,400 --> 00:18:50,860 compete afterwards when you have more time. 316 00:18:50,860 --> 00:18:52,590 Okay? So, the TSP is discussed in a lot of 317 00:18:52,590 --> 00:18:55,290 details in the local search and in the MIP lectures and you can use some of 318 00:18:55,290 --> 00:18:58,980 these techniques while solving it. Okay. 319 00:18:58,980 --> 00:19:01,626 So, keep up with good work and you know, it's really fun looking at, you know, 320 00:19:01,626 --> 00:19:04,440 what you guys are doing and look at the three lectures if you are interest, you 321 00:19:04,440 --> 00:19:08,890 know, on the left of that curve and we want to bring you on the right. 322 00:19:08,890 --> 00:19:12,175 Okay? Great, thank you.