BLAS Level 1 Routines That Can Work With Sparse Vectors

The following BLAS Level 1 routines will give correct results when you pass to them a compressed-form array x(with the increment incx=1):

?asum: sum of absolute values of vector elements
?copy: copying a vector
?nrm2: Euclidean norm of a vector
?scal: scaling a vector
i?amax: index of the element with the largest absolute value for real flavors, or the largest sum |Re(x(i))|+|Im(x(i))| for complex flavors.
i?amin: index of the element with the smallest absolute value for real flavors, or the smallest sum |Re(x(i))|+|Im(x(i))| for complex flavors.

The result i returned by i?amax and i?amin should be interpreted as index in the compressed-form array, so that the largest (smallest) value is x(i); the corresponding index in full-storage array is indx(i).

You can also call ?rotg to compute the parameters of Givens rotation and then pass these parameters to the Sparse BLAS routines ?roti.