1 00:00:05,480 --> 00:00:06,654 Hi, welcome to this new video. 2 00:00:06,654 --> 00:00:11,436 We're going to continue working on our ecosystem simulation, and at this point, 3 00:00:11,436 --> 00:00:15,584 we're going to be starting to talk about how do we remove herbivores from 4 00:00:15,584 --> 00:00:16,534 the system. 5 00:00:16,534 --> 00:00:19,318 What would be the conditions for them to die, right? 6 00:00:19,318 --> 00:00:23,611 We could create a condition in which they die out of the lifespan, 7 00:00:23,611 --> 00:00:28,718 reaching kind of a point where we think that's kind of the end of their life. 8 00:00:28,718 --> 00:00:33,730 But we could also start thinking of how we can connect ideas of feeding or 9 00:00:33,730 --> 00:00:37,404 like achieving a resource like our food system, and 10 00:00:37,404 --> 00:00:42,342 how starvation might happen if that resource is not around, right? 11 00:00:42,342 --> 00:00:47,263 So we really want to create kind of a symbiosis between our different classes 12 00:00:47,263 --> 00:00:49,174 at this point, right? 13 00:00:49,174 --> 00:00:54,122 So what would be our starvation or death from starvation function? 14 00:00:54,122 --> 00:00:58,622 As we have done before, we're going to create a variable that is going to be our 15 00:00:58,622 --> 00:01:02,904 patient value, that is only going to start counting once the animal is in 16 00:01:02,904 --> 00:01:05,266 sick food state or hungry, right? 17 00:01:05,266 --> 00:01:07,431 Maybe when it's in that state, 18 00:01:07,431 --> 00:01:13,114 it will start gradually building up a sense of maybe desperation for food. 19 00:01:13,114 --> 00:01:19,418 That's perhaps how resilient the animal would maintain the search for food. 20 00:01:19,418 --> 00:01:24,115 If it doesn't find any food, especially when there's a lot of competition, 21 00:01:24,115 --> 00:01:26,473 it might end up in a dead state, right? 22 00:01:26,473 --> 00:01:29,554 We're going to remove those entities from the system. 23 00:01:29,554 --> 00:01:35,770 So with this in mind, let's just jump into the code and see how to implement this. 24 00:01:35,770 --> 00:01:37,770 So let's recap where we're at. 25 00:01:37,770 --> 00:01:41,066 We're actually continuing from our last video. 26 00:01:41,066 --> 00:01:44,433 If you remember, in the last video, we have our herbivore, 27 00:01:44,433 --> 00:01:48,114 only a single herbivore in the screen, it's wandering around. 28 00:01:48,114 --> 00:01:51,303 You can see in the console, at some point it transitions to seeking food, and 29 00:01:51,303 --> 00:01:52,934 at that point transitions to resting. 30 00:01:54,914 --> 00:01:57,914 So what I would like to do is kind of bring back a few things. 31 00:01:57,914 --> 00:02:04,634 We're going to create a transition first from resting to wandering, right? 32 00:02:04,634 --> 00:02:06,434 We don't have that yet. 33 00:02:06,434 --> 00:02:11,118 And now that when we have that complete circularity, we're going to introduce 34 00:02:11,118 --> 00:02:15,754 the possibility of this herbivore to die of starvation, right? 35 00:02:15,754 --> 00:02:18,924 And we're also going to bring back many herbivores to the system. 36 00:02:18,924 --> 00:02:24,392 So let's start with the, I'm here in the herbivore class, which is again the class 37 00:02:24,392 --> 00:02:29,548 that we've been working through the weeks, through the different lessons. 38 00:02:29,548 --> 00:02:33,822 If we go down to the rest function, you see that right now we 39 00:02:33,822 --> 00:02:38,596 have a placeholder that says, just print line, I'm resting. 40 00:02:38,596 --> 00:02:40,180 And that's what we can see here in the console. 41 00:02:40,180 --> 00:02:44,364 Our herbivore is in fact only resting, right? 42 00:02:44,364 --> 00:02:46,044 But I'm going to need a few variables first. 43 00:02:46,044 --> 00:02:47,940 Let's create a few variables that we will need. 44 00:02:47,940 --> 00:02:52,238 We did have hunger_level, hunger_threshold. 45 00:02:52,238 --> 00:02:56,760 Let's create a few variables that would be useful to 46 00:02:56,760 --> 00:03:01,910 calculate the starvation and also the rest level, right? 47 00:03:01,910 --> 00:03:05,806 So imagine you're resting and you're kind of regenerating a sense of kind fo rest. 48 00:03:05,806 --> 00:03:08,674 So let's call first self.rest_level. 49 00:03:11,134 --> 00:03:15,314 And that's going to be, we're going to start with something like 0, I think. 50 00:03:16,784 --> 00:03:20,136 Let's just go with 0 for now. 51 00:03:20,136 --> 00:03:25,284 And we're also going to use self.rest_threshold. 52 00:03:27,544 --> 00:03:31,135 And we're going to put a number 50 here for 53 00:03:31,135 --> 00:03:35,688 now so that the sleeping time is not going to be too much. 54 00:03:35,688 --> 00:03:39,344 This is basically how long to sleep for. 55 00:03:39,344 --> 00:03:43,249 If you want that nap to be very long after eating, 56 00:03:43,249 --> 00:03:46,442 you will have to increase this number. 57 00:03:46,442 --> 00:03:49,834 But we're going to spend a bit of time in calibration after this video. 58 00:03:49,834 --> 00:03:55,903 And I will come back here where we're going to create the starvation level and 59 00:03:55,903 --> 00:04:00,333 the starvation threshold, which is going to be a similar 60 00:04:00,333 --> 00:04:04,522 technique to calculate the starvation function. 61 00:04:04,522 --> 00:04:06,594 But for now, let's do the rest. 62 00:04:06,594 --> 00:04:11,524 So resting, we have basically this function here, which is a placeholder. 63 00:04:11,524 --> 00:04:19,404 And we're going to say self.rest_level += 1, right? 64 00:04:19,404 --> 00:04:22,244 So we increase this as a counter. 65 00:04:22,244 --> 00:04:28,113 And if the self.rest_level 66 00:04:28,113 --> 00:04:37,039 is bigger than the self.rest_threshold, 67 00:04:40,605 --> 00:04:42,424 Right, what happens? 68 00:04:42,424 --> 00:04:44,176 That's not how you spell threshold. 69 00:04:44,176 --> 00:04:46,524 There we go, threshold. 70 00:04:49,304 --> 00:04:50,872 We are going to do a few things. 71 00:04:50,872 --> 00:04:52,520 We're going to change the state, right? 72 00:04:52,520 --> 00:05:01,212 So we're going to say self.isAwake = True, right? 73 00:05:01,212 --> 00:05:02,444 So we wake up. 74 00:05:02,444 --> 00:05:05,504 So we are rested enough, we wake up. 75 00:05:06,964 --> 00:05:10,188 We're also going to reset the rest_level. 76 00:05:10,188 --> 00:05:13,104 So now the rest_level goes back to 0. 77 00:05:17,404 --> 00:05:21,310 And finally, and perhaps the most important part, 78 00:05:21,310 --> 00:05:23,972 is that we reset the tree, right? 79 00:05:23,972 --> 00:05:28,107 What we do here in other functions, like whenever we want to reset 80 00:05:28,107 --> 00:05:33,292 the calculation of the decision tree, we go back and recalculate that the current 81 00:05:33,292 --> 00:05:37,864 node of the tree, the decision tree, will become a new calculation. 82 00:05:37,864 --> 00:05:41,701 So this would kind of cascade through the tree, check, is it awake? 83 00:05:41,701 --> 00:05:46,008 Now, it's true, it's going to transition back to a wandering state or 84 00:05:46,008 --> 00:05:50,032 a sick food state, depending on if it's hungry or not hungry. 85 00:05:50,032 --> 00:05:53,724 Most likely after eating and going to a rest, 86 00:05:53,724 --> 00:05:57,604 our herbivore will be, in fact, not hungry. 87 00:05:57,604 --> 00:06:01,156 So it would probably default back to a wandering state, right? 88 00:06:01,156 --> 00:06:03,790 So, but again, it's important to debug and 89 00:06:03,790 --> 00:06:06,724 make sure that your behavior is as you expected. 90 00:06:06,724 --> 00:06:08,870 Sometimes you might, depending on the order of things, 91 00:06:08,870 --> 00:06:10,604 you might be getting a different result. 92 00:06:10,604 --> 00:06:12,404 So we are in a wandering state. 93 00:06:12,404 --> 00:06:14,068 Let's just check that this is working. 94 00:06:14,068 --> 00:06:15,252 Seeking food. 95 00:06:15,252 --> 00:06:19,064 Now it's resting, going back to wandering, right? 96 00:06:19,064 --> 00:06:20,296 And now it's wandering around. 97 00:06:20,296 --> 00:06:21,920 It's not necessarily seeking that food. 98 00:06:21,920 --> 00:06:22,832 It's not hungry yet. 99 00:06:22,832 --> 00:06:25,960 Got hungry, went and eat, now wanders around. 100 00:06:25,960 --> 00:06:28,401 So the wander state is more like a curiosity, 101 00:06:28,401 --> 00:06:30,336 kind of hanging out kind of state. 102 00:06:30,336 --> 00:06:34,232 The seeking food is a state of chasing that food. 103 00:06:34,232 --> 00:06:36,176 So we have that circularity, right? 104 00:06:36,176 --> 00:06:41,064 It loops around three different states. 105 00:06:41,064 --> 00:06:46,041 Let's bring back in the World_Manager, remember that we actually 106 00:06:46,041 --> 00:06:50,812 created a single herbivore with this function as a placeholder. 107 00:06:50,812 --> 00:06:55,510 So I'm going to remove all that because now I actually would like to create 108 00:06:55,510 --> 00:06:57,204 herbivores over time. 109 00:06:57,204 --> 00:07:02,148 And we did that thing with this function here that we had commented out, right? 110 00:07:02,148 --> 00:07:04,864 So every 80 frames we create a new herbivore. 111 00:07:06,404 --> 00:07:08,644 Let's just see how that would work. 112 00:07:08,644 --> 00:07:14,004 So we have one here, and every time we create a new herbivore, 113 00:07:14,004 --> 00:07:18,244 this is a pretty high rate of population growth. 114 00:07:19,864 --> 00:07:23,812 And you can see all of them are kind of eating the food supply that is available 115 00:07:23,812 --> 00:07:24,784 close to them. 116 00:07:24,784 --> 00:07:29,682 At some point, they will run out of food because 117 00:07:29,682 --> 00:07:33,944 the food kind of grows at its own rate. 118 00:07:33,944 --> 00:07:39,344 But suddenly more and more herbivores are getting hungry and they're not being fed. 119 00:07:40,604 --> 00:07:44,204 And eventually, they're going to reach a point where they cannot find the food. 120 00:07:44,204 --> 00:07:49,904 They're kind of chasing, chasing, chasing, and they're not going to find their food. 121 00:07:51,484 --> 00:07:53,981 At that point, we should be killing them, or 122 00:07:53,981 --> 00:07:57,796 basically they should be dying from not really having enough food. 123 00:07:57,796 --> 00:08:00,511 So that's where our starvation function is going to kick in, right? 124 00:08:00,511 --> 00:08:05,740 So let's just make sure that we go all the way up here to the herbivore node, 125 00:08:05,740 --> 00:08:10,975 and let's create another variable that is going to be our starvation value. 126 00:08:19,968 --> 00:08:24,118 And it's going to start at 0, and 127 00:08:24,118 --> 00:08:33,899 starvation_threshold, It's going to say 100. 128 00:08:33,899 --> 00:08:38,417 So for 100 frames, if our herbivore looks for food for 129 00:08:38,417 --> 00:08:43,424 100 frames and it doesn't find food, it will die, right? 130 00:08:44,484 --> 00:08:49,452 So now that we have those variables, let's just put them in action. 131 00:08:49,452 --> 00:08:54,900 We're going to be looking into the seek_food function. 132 00:08:54,900 --> 00:08:57,504 That's basically where we want the starvation to kick in. 133 00:08:58,684 --> 00:09:01,782 So sick food, why do we want to do it in the seeking food? 134 00:09:01,782 --> 00:09:05,732 Because we want to make sure that while we're looking for food, 135 00:09:05,732 --> 00:09:09,366 the particular kind of movement that is faster, right? 136 00:09:09,366 --> 00:09:12,470 We're exerting more energy for looking food. 137 00:09:12,470 --> 00:09:13,598 It's kind of a desperate mode. 138 00:09:13,598 --> 00:09:18,194 It's like we're competing against other herbivores for food at this point. 139 00:09:19,334 --> 00:09:22,462 At this point, we're going to kick in a sense of like, 140 00:09:22,462 --> 00:09:25,502 now you're a countdown of starvation, right? 141 00:09:25,502 --> 00:09:30,593 So we would do the same technique again of 142 00:09:30,593 --> 00:09:36,332 self.starvation _value += 1, right? 143 00:09:36,332 --> 00:09:38,964 So your starvation will start growing. 144 00:09:38,964 --> 00:09:43,001 And if that starvation_value, 145 00:09:45,341 --> 00:09:50,583 It's bigger than the starvation_threshold, 146 00:09:50,583 --> 00:09:55,964 which we, I think we said 100 frames, right? 147 00:09:56,984 --> 00:10:01,636 We're going to call a function like die, [LAUGH] right? 148 00:10:01,636 --> 00:10:06,936 And we don't have that function yet, so let's create it. 149 00:10:06,936 --> 00:10:12,504 So def die(), it's going to take self. 150 00:10:12,504 --> 00:10:18,496 And here how we have done this before, like food actually can remove itself. 151 00:10:18,496 --> 00:10:21,464 It could be eaten, so it could be removed. 152 00:10:21,464 --> 00:10:25,546 We need to make sure that we have a reference to, currently, 153 00:10:25,546 --> 00:10:30,544 the herbivore has a reference to the all_food variable, right? 154 00:10:30,544 --> 00:10:34,129 So it can understand where all the food elements are, but it doesn't understand 155 00:10:34,129 --> 00:10:36,923 its position in relation to a population of other herbivores, 156 00:10:36,923 --> 00:10:39,280 especially because those are part of a list as well. 157 00:10:39,280 --> 00:10:42,617 So we're going to do here all_herbivores, 158 00:10:46,258 --> 00:10:51,228 And so all_herbivores will be a passing of the list that 159 00:10:51,228 --> 00:10:56,304 contains all the herbivores, or death is going to be like, 160 00:10:56,304 --> 00:11:01,320 you're no longer computed as part of that collection. 161 00:11:01,320 --> 00:11:03,644 You're removed from that collection in a way. 162 00:11:04,904 --> 00:11:11,104 So let's also, when we did self.all_food, where is that all_food? 163 00:11:11,104 --> 00:11:12,048 There, here. 164 00:11:12,048 --> 00:11:14,924 So let's do the same thing. 165 00:11:18,884 --> 00:11:24,028 self.all_herbivores = all_herbivores, right? 166 00:11:24,028 --> 00:11:28,307 So if we do that, because we changed the construction of the class, 167 00:11:28,307 --> 00:11:32,510 we need to make sure that whenever we're creating the class here, 168 00:11:32,510 --> 00:11:36,868 we're constructing a herbivore, we're passing on all_food. 169 00:11:36,868 --> 00:11:44,401 We also have to pass all_herivores, which is the list, right? 170 00:11:44,401 --> 00:11:50,549 And the constructor demands a series of arguments, right? 171 00:11:50,549 --> 00:11:56,464 And now we're passing the list of herbivores to the herbivore class, right? 172 00:11:57,644 --> 00:11:59,684 So that's our node. 173 00:11:59,684 --> 00:12:03,748 So now that we have all the herbivores referenced, we can actually die or 174 00:12:03,748 --> 00:12:05,460 kind of kill the herbivore. 175 00:12:05,460 --> 00:12:10,696 This function here, as we have discussed, 176 00:12:10,696 --> 00:12:16,779 or the same way in which we have done it for the food, 177 00:12:16,779 --> 00:12:26,104 right, which is self.all_herbivores.remove(self), right? 178 00:12:26,104 --> 00:12:30,778 And with that function now written, 179 00:12:30,778 --> 00:12:37,423 we can do self.die within the seek_food, right? 180 00:12:37,423 --> 00:12:41,694 So if the starvation level reaches, we're going to find a dead state, 181 00:12:41,694 --> 00:12:44,036 removing yourself from the system. 182 00:12:44,036 --> 00:12:47,068 So you would imagine that the more herbivores you have in 183 00:12:47,068 --> 00:12:48,892 the system competing for food. 184 00:12:48,892 --> 00:12:52,568 Some of them will be maybe further away from food and will transition to look for 185 00:12:52,568 --> 00:12:55,620 another piece of food, and eventually some of them will die. 186 00:12:55,620 --> 00:13:00,401 So they will start creating kind of this dynamic equilibrium between the amount of 187 00:13:00,401 --> 00:13:03,728 food available and the amount of herbivores available, 188 00:13:03,728 --> 00:13:08,303 because the herbivores are not going to be able to sustain population growth that 189 00:13:08,303 --> 00:13:11,104 doesn't have any food supply, right? 190 00:13:11,104 --> 00:13:16,824 So let's just see if our simulation is running correctly. 191 00:13:16,824 --> 00:13:19,769 So we have herbivores running around, 192 00:13:19,769 --> 00:13:25,104 they're getting hungry, and they start eating the food. 193 00:13:25,104 --> 00:13:30,648 And eventually some of them, we currently don't have a very clear way. 194 00:13:30,648 --> 00:13:33,844 You see one of them, I think, disappeared here. 195 00:13:33,844 --> 00:13:37,640 You might want to create a state, not just remove them from the system, but 196 00:13:37,640 --> 00:13:40,452 you see that some of them just disappear, they die. 197 00:13:40,452 --> 00:13:43,676 Our death is kind of pretty quick and pretty brutally. 198 00:13:43,676 --> 00:13:48,292 You don't see them really hanging around in any way. 199 00:13:48,292 --> 00:13:50,636 They just disappear. 200 00:13:50,636 --> 00:13:52,588 So we remove them from the computation. 201 00:13:52,588 --> 00:13:57,016 What we could actually do, if you wanted to graphically see them stay around, 202 00:13:57,016 --> 00:14:01,781 you can actually reduce their speed, maybe as they get tired, or you could actually 203 00:14:01,781 --> 00:14:06,814 leave them in a dead state as part of a computation, but maybe without an emotion. 204 00:14:06,814 --> 00:14:11,110 So it could be visible that how many of your animals 205 00:14:11,110 --> 00:14:14,734 are actually not surviving, right? 206 00:14:14,734 --> 00:14:17,802 But we're going to spend a bit of time in the next video really calibrating and 207 00:14:17,802 --> 00:14:18,766 also visualizing. 208 00:14:18,766 --> 00:14:23,421 There's a lot of data going on here that it might be important to visualize so that 209 00:14:23,421 --> 00:14:28,154 we could actually visually debug if our system is performing the way we intended. 210 00:14:29,184 --> 00:14:31,080 We're going to leave this video here, and I'll see you in the next one. 211 00:14:31,080 --> 00:14:32,648 We're going to be doing that visualization. 212 00:14:32,648 --> 00:14:33,148 I'll see you then.