Introduction to Concurrency in Programming Languages

Performance Considerations and Modern Systems 195

its four neighbors (up, down, left, right), where the boundaries wrap

around (e.g., the upper neighbor of array elements on the top row are

the elements in the same column on the bottom row).

Measure the amount of time required to execute a number of iterations

of the doubly nested loop. Now, switch the indices that each loop corre-

sponds to and measure how the timing of the loop changes. Discuss what

you see in relation to row-versus-column major ordering and caches.

3. Using the example of cooking a meal in the introduction, identify the

parts of the process of preparing the meal that are inherently sequential

and those that can be parallelized. How does Amdahl’s law impact show

up in real-world