in linq why are subsequent calls of IEnumerable.Intersect so much faster

Question

while looking at this question C# Similarities of two arrays it was noted that the initial linq call was significantly slower than subsequent calls. What is being cached th

Answer 1

I would expect the first run of any loop to be slower for three reasons:

1. Code has to be jitted the first time, but not subsequently.
2. If the executable code run is small enough to fit in cache, then it won't have been evicted, and be faster for the CPU to load.
3. If the data is small enough to fit in cache, then it won't have been evicted, and be faster for CPU to load.