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)

cblas_?asum: sum of absolute values of vector elements
cblas_?copy: copying a vector
cblas_?nrm2: Euclidean norm of a vector
cblas_?scal: scaling a vector
cblas_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.
cblas_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-1]

; the corresponding index in full-storage array is

indx[i-1]

You can also call

to compute the parameters of Givens rotation and then pass these parameters to the Sparse BLAS routines

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