1 | s = s + a(i)*b(i) on x86 requires that one stores and restores both a(i)*b(i) and s to memory after arithmetic. There is clever way of using exception trap to speed up. |
2 | Indigenous type would specify most precise floating point representation allowed by hardware |
3 | anonymous double would imply all intermediate results implemented using double precision (original C standard) |
4 | anonymous indigenous would instruct compiler to use extended double precision on x86 chips for all computations -- whatever type of variable |