What is a scenario in which barrier synchronisation might be advantageous?

Determination of the critical path is required for the following network diagram:

What is an application that would benefit from the use of barrier synchronization.

What does the intractable nature of the halting issue imply?

How do "Redundant Arrays of Independent NAND" (RAIN) enhance SSD reliability?

Explain what phantom arms are and why they happen. Why is it possible that this could lead to bad concurrent processing even though the two-phase synchronisation method is being used?

Compute the capacity and input distribution attaining it for the discrete memoryless channel X → Y with X = y = {0, 1, 2, 3} given by Y = X + Z mod 4, where Z takes on values from Z = {0, 1, 2, 3} with z(0) = 1/2, z(1) = 0, and z(2) = z(3) = 1/4.

I'm confused as to what the problem with NRZ is. To what extent is this a problem, and more importantly, how can it be resolved?

1) Given an O/S with soft timers using a single clock, consider a situation where the event list looks like this:   Current time = 4105; Next Signal = 6; Clk Header → 6 → 1 → 3 → 12 → 5 a. What will current time be when the “12” signal is dispatched =  b. At time 4113 a new signal arrives to be scheduled for 4125, fill in the following to reflect this signal being added at that time:        Current time = ; Next Signal = ; Clk Header → 2)  Given a disk with 100 tracks, Consider the following disk request sequence (track numbers): 45, 20, 90, 10, 50, 60, 80, 25, 70. The initial position of the R/W head is on track 50. Determine the distance that will be traversed by the R/W head when the Shortest Seek Time First (SSTF) algorithm is used and the Elevator algorithm (note -the Elevator algorithm will move towards 100 when it starts execution).  Which algorithm will move the fewest tracks , SSTF or Elevator: , and by how many fewer tracks: tracks less than the other algorithm.

Question is in the image, Give a detailed explanation for the answer