Please clarify the bit about the algorithm. You mention (23:14) that D-TM has three tapes. Tape two and three are empty. Tape two is used to simulate the computation for each branch of N-TM. Thus tape three would need to contain the complete address to follow said branch. So does that mean tape three contains the sequence of {1,2,3}* produced by a BFS? How does tape three acquire this address if the N-TM has a branch that loops forever?
Tape three start by containing nothing and slowly increment for each choice in a simulation. If ,let's say, 3 braches are possible at a given time, tape three will first contain "1", then the second simulation it will contain "2", then "3", then "11", "12", "13", "21", "22", "23", "31", "32", "33", etc. Because a breadth first order is used, first all possibilities on a level of the tree are simulated. If an ACCEPT state is encountered, the D-TM will halt and accept. When the N-TM loops, as you mentioned, the breadth first technique will keep exploring these paths infinitely and thus the D-TM also loops. The D-TM only halts when an accept state is encountered or when all possible paths have been explored (in other words: when all branches of the N-TM reject).
This video is a gem. I was facing a lot of difficulties understanding this, but you made it very easy. Thank you!
Please clarify the bit about the algorithm. You mention (23:14) that D-TM has three tapes. Tape two and three are empty. Tape two is used to simulate the computation for each branch of N-TM. Thus tape three would need to contain the complete address to follow said branch. So does that mean tape three contains the sequence of {1,2,3}* produced by a BFS? How does tape three acquire this address if the N-TM has a branch that loops forever?
Tape three start by containing nothing and slowly increment for each choice in a simulation. If ,let's say, 3 braches are possible at a given time, tape three will first contain "1", then the second simulation it will contain "2", then "3", then "11", "12", "13", "21", "22", "23", "31", "32", "33", etc.
Because a breadth first order is used, first all possibilities on a level of the tree are simulated. If an ACCEPT state is encountered, the D-TM will halt and accept.
When the N-TM loops, as you mentioned, the breadth first technique will keep exploring these paths infinitely and thus the D-TM also loops.
The D-TM only halts when an accept state is encountered or when all possible paths have been explored (in other words: when all branches of the N-TM reject).
Excellent teacher!
much better than most videos!
Very clear. Thanks!
you are amazing
Very helpful! Thanks mate! XD
If possible please upload the notes you used to explain as pdf and share the link in the playlist description.It would really be helpful.
thank you , it was grate!
please if you could upload your videos in higher quality, 240p is so hard to read