why there is no "non-absolute" version of cublasDasum in cublas to sum up the elements of

I want to sum up the elements of an array. I know that I can use reduction, but it is a little difficult for me to fully understand it. I saw that in cublas, there is this function called cublasDasum that sums up the absolute values of the elements. It seems there should be a very similar function that sums up the elements, not the absolute values. Is there any way I can find the source code of cublasDasum and see how this is done?