Timing of array initialisation

[ashe]

@Arjen

While I am not a compiler writer, I can make a guess at the timings: in the second case the program needs to make a temporary array, fill it and then copy it into the target array on the lefthand-side.

This is what gfortran seems to do, even with -O3. It dynamically allocates a temp, fills it in, and copies into buildarray.

But since this can be done at compile-time, you probably have a case where the compiler does the heavy work and stores the result in the object file (.o).

This is what flang does, with both versions of the initialization. It takes a long time to create the .o file but at runtime it just copies from static memory into the result.