Why does element-wise addition in two separate loops work faster than in one combined loop?

Hi everyone! I've been writing in C++ for a couple of months, and I encountered very strange performance behavior. There are two arrays: `a` and `b` of size 200000000 elements (about 800 MB each). I want to add them element-wise and store the result in array `c`, then multiply each element of `c` by 2 and store in `d`. I wrote two code variants: **Variant 1 (two separate loops):** ```cpp for (int i = 0; i < n; ++i) { c[i] = a[i] + b[i]; } for (int i = 0; i < n; ++i) { d[i] = c[i] * 2; } ``` **Variant 2 (one combined loop):** ```cpp for (int i = 0; i < n; ++i) { c[i] = a[i] + b[i]; d[i] = c[i] * 2; } ``` I expected the second variant to be faster since it does everything in one pass. But in practice (MSVC compiler, /O2 flags, x64 architecture) the first