What can make a program run slower when using more threads?

Question

This question is about the same program I previously asked about. To recap, I have a program with a loop structure like this:

for (int i1 = 0; i1 < N; i1+         


        

Answer 1

Off the top of my head:

• Context switches
• Resource contention
• CPU contention (if they aren't getting split to multiple CPUs).
• Cache thrashing