While examining the children of a maximizer, if v of maximizer > beta, prune the rest of the children. While examining the children of a minimizer, if v of minimizer < alpha, prune the rest of the children.
+Dinh Hung Nguyen Attention please at minute 2:28 !!! Hello :) Thank you very much for your explaination. It is very helpful. The algorithm checks whether the value 4 is higher or equal !!! to beta. Thank you, BR
Some important notes: 1) only in a Max node can update the corresponding alpha, so does Min for beta. 2) v can only be returned up to its parent 3) alpha and beta can only be passed down from its parent 4) cut the current node from the tree whenever alpha >= beta
Thanks for the video! Even though this is a relatively simple algorithm, the only way to really understand it is to go step by step on a toy problem, like you did. Excellent job!
I found this very helpful especially once the values of alpha and beta weren't just infinity and -infinity! I kept pausing the video and working through a couple steps then playing the video to see if I did them right, which really helped me grasp when you change the values of alpha and beta. Great video although it did take me a couple watches to fully get it!
A very good explanation. A lot of people are complaining about how this could be more simple, but look at the title, it shows you if how exactly algorithm would do this.
Pretty good explanation. I think the hard to get part, for me, is the best path to the root concept. But if one works through some trees, I think it becomes more clear.
Congratulations, very well explained. It was very usefull for me. I agree there is not much tutorials which explain this concept as u do. Again, congratulations and thank you man.
To be honest, I found MIT's lecture is a little bit better. The lecturer at MIT (Patrick Winston) provides more intuition behind the alpha beta pruning, while Prof Pieter Abbeel, although shows clear logic behind each step, does not give us reson for why you should do this, and the example is a bit complicated as well. So I personally recommend watching the MIT's AI lecture 6 at first, then watching this.That would be a perfect complement.
How do you know the nodes are sorted like this such that the max/min knows to prune vs the other node being possibly lower on the same depth pair? (Like when 7 prunes 9 and it was swapped order)
Anyone else following the General Game Playing course on Coursera? The Alpha-Beta Search was by far the most confusing one (because of lack of an example) so far in the lectures and this helped a lot.
+moraigna66 Also, there was a lack of a well defined system. No where it mentions how the alpha must only come from "above" for a minimizer but the same minimizer can use a beta from a previously explored "lower" branch and vice-versa for the maximizer.
Very well detailed explanation of alpha beta pruning given Sir! You are really a good teacher, saved me from this confusing algo! I was tearing my hair getting to understand this, until i came over to your video. Thank you so much!
Thanks a lot! I understand it much better now :) btw, i have a strange question: how do u write on the screen? is it a special digital pen? thanks again :)
Great tutorial, really helped me. But why are alpha and beta passed to leaf nodes? Is this because they're passed before we know its a leaf when implemented?
In the branch to the right, alpha is already set to 6. This means that the v should be set to 6 initially in the max-nodes, not -infinity as is shown in the video. If you find this hard, look up the minmax algorithm. Alpha-beta is built upon minmax
Which part, or what aspects lost you? This stuff always seems like magic at first, but asking questions, discussion, and going t/ examples really helps. I've been trying a few problems before this video, and it really helped make some of the steps click.
It's well explained it even has to much info, like addition of minimizer at the (main) root. But if you don't understand this I suggest dodging any kind of algorithm based courses in the future
Wait. Why isn't beta changed in the middle tree with 2 as its maximizer? When 2 is the max for the node, wouldn't it be propagated up to the minimizer node? Alpha isn't changed but shouldn't beta be changed from +inf to 2? And since alpha > beta, the whole right subtree is pruned.
A little bit messy But still 100 times better than my University's AI lecturer My understandeing: When a maximizer is going to look at other children, check if it already has a value that is greater than the best minimizer value along its way to root, you can stop it because the only thing it can do is to make this value more than the current value, however the current value is already greater than the best minimizer value, so the upper minimizer will discard this node anyways. Same thing to a minimizer, if it discovers its value is already smaller than the best maximizer value, you can stop it from expanding, because the only thing it can do is to keep lowering that value and it will be discarded later.
9:05 : How are we so sure that there is a lower value in the next branch, thus pruning this branch? I lack the understanding of how you come to that conclusion. If anyone could clear that up for me, I thank you so much.
+1stMusic Ah, it's not that there's a value less than 2 in the right branch, it's that the minimizer has has the option to choose 2 at that node (and possibly a lower value than 2 if it turns out that the right branch does have a lower value). Since the minimizer has the ability to choose a 2 (or maybe lower) in the main center branch, the maximizer would compare the value of 2 with the value of 6 to see which is higher. If the maximizer chooses the center branch then the minimizer would be able to force a game value of 2 or less; however if the maximizer chooses the left branch then the minimizer only has the ability to force a value as low as 6. thus the maximizer will only want to choose the left branch at that point, no matter what other unexplored values there are in the center branch. Hope that helped if you were still wondering about that.
it makes sense, but classifying the variable as internal structure of a node would've simplified your explanation greatly, and explaining that there appears to be two forms of pruning, local pruning and greater pruning, local where the local scope of an object is taken into account, in the first instance of the prune shown in this video; and the second where the tactical decision to circumvent this option was taken because no matter what option the maximizer presented to the minimizer the minimizer would've taken the value 2 or lower; as thats where it seems you confused alot of people. note i'm not stating there are different prunes, they use the same strategy just the reasoning behind the prune is different which i've represented with different names.
a good student need not be a good teacher. to become a really good teacher, you need to spend 10 times more time thinking what is the best innovative way so that my students can grasp this concept easily.
At around 2:22 to 2:29, Pieter says "for that it checks the following conditions: it checks whether this value of 4, the current value here is higher than beta. If that's the case, then it doesn't need to look at any further children here..." He should have said "...higher than OR EQUAL TO beta."
While examining the children of a maximizer, if v of maximizer > beta, prune the rest of the children.
While examining the children of a minimizer, if v of minimizer < alpha, prune the rest of the children.
💯
You saved my ass right before my A.I exam
+Dinh Hung Nguyen yeah
+Dinh Hung Nguyen
Attention please at minute 2:28 !!!
Hello :)
Thank you very much for your explaination.
It is very helpful.
The algorithm checks whether the value 4 is higher or equal !!! to beta.
Thank you, BR
i have an AI exam in a few hours lol
me 2
Some important notes:
1) only in a Max node can update the corresponding alpha, so does Min for beta.
2) v can only be returned up to its parent
3) alpha and beta can only be passed down from its parent
4) cut the current node from the tree whenever alpha >= beta
Thanks man that helped A LOT .
Thanks for the video! Even though this is a relatively simple algorithm, the only way to really understand it is to go step by step on a toy problem, like you did. Excellent job!
one advice: Keep it clean and clear !!
If you understand the minima concept, this is an awesome explanation and it really helped me a lot. Thank you
I found this very helpful especially once the values of alpha and beta weren't just infinity and -infinity! I kept pausing the video and working through a couple steps then playing the video to see if I did them right, which really helped me grasp when you change the values of alpha and beta. Great video although it did take me a couple watches to fully get it!
This video helped me understand pruning better thank you! Those of you complaining abt how messy it is, draw it yourself as he goes along.
A very good explanation. A lot of people are complaining about how this could be more simple, but look at the title, it shows you if how exactly algorithm would do this.
Pretty good explanation. I think the hard to get part, for me, is the best path to the root concept. But if one works through some trees, I think it becomes more clear.
this makes a lot of sense if you've already seen this like at least a dozen times. if you're new, don't even waste time watching this
6 hours before the exam and I'm studying now. Why am I like this
I know it makes sense and all, but it sure does take a few minutes for it to sink in and stick. Glad you went through the entire process.
Congratulations, very well explained. It was very usefull for me.
I agree there is not much tutorials which explain this concept as u do.
Again, congratulations and thank you man.
To be honest, I found MIT's lecture is a little bit better. The lecturer at MIT (Patrick Winston) provides more intuition behind the alpha beta pruning, while Prof Pieter Abbeel, although shows clear logic behind each step, does not give us reson for why you should do this, and the example is a bit complicated as well. So I personally recommend watching the MIT's AI lecture 6 at first, then watching this.That would be a perfect complement.
Thank you for sharing. I understand better now.
Yes you are absolutely right, he explains it much better!
Yup, watch the MIT lecture first then this one! Helps so much
exactly......followed your sequence ........helped a lot
Agree, you are correct. The lecture explained better than this guy. Maybe I was a dumb or something. Can't get this video's idea T^T
This is a great explanation. I am shocked to see that some people disliked this video....
Thanks :) Currently working on this in my AI class and this helped a lot.
How do you know the nodes are sorted like this such that the max/min knows to prune vs the other node being possibly lower on the same depth pair? (Like when 7 prunes 9 and it was swapped order)
you dont know how much u saved me. thanks so much man
wish i could hit like button 100 millions times
thanks man God bless yuh
peace
Anyone else following the General Game Playing course on Coursera?
The Alpha-Beta Search was by far the most confusing one (because of lack of an example) so far in the lectures and this helped a lot.
+moraigna66 Also, there was a lack of a well defined system. No where it mentions how the alpha must only come from "above" for a minimizer but the same minimizer can use a beta from a previously explored "lower" branch and vice-versa for the maximizer.
This is a really well explained video. Thanks Pieter
Excellent walk through!
Thank you Thank you Thank you :)))
Very very helpful for Computer Engineer
Very well detailed explanation of alpha beta pruning given Sir! You are really a good teacher, saved me from this confusing algo! I was tearing my hair getting to understand this, until i came over to your video. Thank you so much!
Worst teacher
why? You didnt understand the explanation? :(
Nope. Nada.
:-(
Thanks a lot! I understand it much better now :)
btw, i have a strange question: how do u write on the screen? is it a special digital pen?
thanks again :)
This is brilliant, much appreciated sir.
Great tutorial, really helped me. But why are alpha and beta passed to leaf nodes? Is this because they're passed before we know its a leaf when implemented?
2:27
should be: current value is higher OR EQUAL than beta
Great video! I finally understood how alpha-beta pruning works! Thanx!
This video helped me very much with my Artificial Intelligence course. Thank you for taking the time to make this video.
Wonderfully explained. Thanks a lot!
Thank you. This helped me a lot !!
In the branch to the right, alpha is already set to 6. This means that the v should be set to 6 initially in the max-nodes, not -infinity as is shown in the video. If you find this hard, look up the minmax algorithm. Alpha-beta is built upon minmax
Always initiate unexplored max node to -infinity
First you do this.
Then this.
Then magic.
More magic.
Done. Do you understand now?
are you kidding me?? or are you a kid in real??? best explained ? where is deep cutting you dumb??
Which part, or what aspects lost you? This stuff always seems like magic at first, but asking questions, discussion, and going t/ examples really helps. I've been trying a few problems before this video, and it really helped make some of the steps click.
It's well explained it even has to much info, like addition of minimizer at the (main) root. But if you don't understand this I suggest dodging any kind of algorithm based courses in the future
that's because the depth is only 4
😂😂
I think that the 6th leaf, the number 2 is wrong, isnt it suposed to be the 6 a better option?
Great video, really helped! (I'm a junior majoring in AI and Robotics)
Hi, what if the first node is negative value? For example, if it is -5?
Wait. Why isn't beta changed in the middle tree with 2 as its maximizer? When 2 is the max for the node, wouldn't it be propagated up to the minimizer node? Alpha isn't changed but shouldn't beta be changed from +inf to 2? And since alpha > beta, the whole right subtree is pruned.
much appreciated, very thorough explanation yet clear and simple.
Thank you! Well done!
Clear as mud
Listen to the explanation around 09:00 . "A maximizer has a better option than two- six" which comes from the previous branch, incidentally.
Crystal clear!
can't thank you enough!
Thanks a ton!!! appreciate it.
Geniusss!!!! You´v saved my work
Great video. Thank you.
Hey thanks for video if we apply alpha beta pruning right to left instead of left to right is it effect the result thank you
Beautiful.
Thank you professor.
Nice speech, could finally understand the concept with of this vid
Thank you very much for the video. It really helped me!
best ever the best the most best fantastic explanation thank you prof.
This was really helpful for me. Thank you!
Thanks very much!
Thank you so much !!
Minute 8:26 why is he sending up 2? instead of 6 which is the highest alfa, beta is still infinity. Dont understand this, is he doing wrong?
Thank so much for saving my final *big thumbs up*
Such a messy explanation, I got more confused than I was before watching this video
A little bit messy
But still 100 times better than my University's AI lecturer
My understandeing:
When a maximizer is going to look at other children, check if it already has a value that is greater than the best minimizer value along its way to root, you can stop it because the only thing it can do is to make this value more than the current value, however the current value is already greater than the best minimizer value, so the upper minimizer will discard this node anyways.
Same thing to a minimizer, if it discovers its value is already smaller than the best maximizer value, you can stop it from expanding, because the only thing it can do is to keep lowering that value and it will be discarded later.
Thank you very much!!!!
Thanks, great explanation!
that video kind of saved my ass. thank you. maybe you can explain when the cut is called a-cut and when it is calles b-cut
This really helped me understand alpha-beta minimax! Thank you so much!
Thanks. Helps lots
thanks a ton! one of the best explanations :)
Great video , very clear .
Nice and simple! Thanks.
Thanks a lot my friend !
amazing explanation!
I thought this would explain prune, the game...
What language are you speaking?
Thanks, you're great
thanks a lot prof.
thank you
nice video,I can understand the notion now.
way too messy
Yes but it does the job
Awesome!
Awesome Explaination!
thank you so much
Perfect!
9:05 : How are we so sure that there is a lower value in the next branch, thus pruning this branch? I lack the understanding of how you come to that conclusion.
If anyone could clear that up for me, I thank you so much.
+1stMusic Ah, it's not that there's a value less than 2 in the right branch, it's that the minimizer has has the option to choose 2 at that node (and possibly a lower value than 2 if it turns out that the right branch does have a lower value). Since the minimizer has the ability to choose a 2 (or maybe lower) in the main center branch, the maximizer would compare the value of 2 with the value of 6 to see which is higher. If the maximizer chooses the center branch then the minimizer would be able to force a game value of 2 or less; however if the maximizer chooses the left branch then the minimizer only has the ability to force a value as low as 6. thus the maximizer will only want to choose the left branch at that point, no matter what other unexplored values there are in the center branch.
Hope that helped if you were still wondering about that.
Tori Knorth Thanks, I got it!
You sir, are a GOD
it makes sense, but classifying the variable as internal structure of a node would've simplified your explanation greatly, and explaining that there appears to be two forms of pruning, local pruning and greater pruning, local where the local scope of an object is taken into account, in the first instance of the prune shown in this video; and the second where the tactical decision to circumvent this option was taken because no matter what option the maximizer presented to the minimizer the minimizer would've taken the value 2 or lower; as thats where it seems you confused alot of people. note i'm not stating there are different prunes, they use the same strategy just the reasoning behind the prune is different which i've represented with different names.
Thanks for this screencast :)
a good student need not be a good teacher.
to become a really good teacher, you need to spend 10 times more time thinking what is the best innovative way so that my students can grasp this concept easily.
At around 2:22 to 2:29, Pieter says "for that it checks the following conditions: it checks whether this value of 4, the current value here is higher than beta. If that's the case, then it doesn't need to look at any further children here..."
He should have said "...higher than OR EQUAL TO beta."
Thanx man!!that was seriously awesome..
Thanks a lot, sir.
THANK YOU SO MUCH
Thank you so much for this video!!!!
Why I can't have a lecturer just like you!!!!!!
got it! thanks a lot.
Thanks a lot, very helpful
OMG tks sir! you save my life !
Only this is clear and accurate tutorial i have found on the internet..today is my AI exam..thanks a lot to you.
Thanks ! Perfect
Pretty much how Dragon Ball tournament was organized
lmao. dbsuper sucked ballz
dragon ballz that is ;)
underrated comment ...
Thanks!
5 rewatches later
Its making sense
Thanks a lot. Well explained!
I am not sure why others did not get it. Maybe if you first check the theory, then watch this, you should get it.