Lecture 7 - Halting Problem

Question 1

The halting problem is ….

Answer 1

undecidable

Question 2

What is the erratic program?

Answer 2

• refer to slide 36
• it is a program that terminates for all instances tested, but can’t be proven to not be a halting problem

Question 3

What does it mean for an algorithm implementation to halt?

Answer 3

The program returns yes or no and isn’t stuck in a while loop

Question 4

What does HP stand for?

Answer 4

Halting problem

Question 5

If a problem can be reduced to another problem and the original problem is undecidable then?

Answer 5

The second problem must too be undecidable

Question 6

Hierarchy of decision problems:

Answer 6

• undecidable (HP,tiling)
• intractable (roadblock)
• NP-COMPLETE (SAT , HC , TSDP)
• polytime solvable

Question 7

What happens if P = NP?

Answer 7

All np complete problems are polynomial time solvable.