$[$Optional$,30$ bonus pts$]$ Implement the C code of the DAXPY loop similar to the one

below and measure its execution time on your computer. Then unroll the loop by a

factor of $4$ and compare the execution time with the time without loop unrolling. Note:

you can use a timing function called "gettimeofday$(...)"$ before and after the for loop

to measure the time accurately.

for

$y[i]=a**x[i]+y[i]$

$\}$