Question

http://ideone.com/vHK8Y why is the macro slower than the function?

Answer 1

This is just an educated guess, but I would say that the isort() function goes through more processing steps than your created (lean) insert_sort function. I don't know enough about C to say for certain though.

Answer 2

try to change the function and let me know then click on here http://www.azillionmonkeys.com/qed/sqroot.html

Answer 3

Depending on the size of your array, the copying of sequence into isort could take some time.