IZAMAX(3) BLAS routine of NEC Numeric Library Collection IZAMAX(3)
NAME
IZAMAX - BLAS level one, maximum index function
SYNOPSIS
INTEGER FUNCTION IZAMAX ( n, x, incx )
INTEGER n, incx
DOUBLE COMPLEX x
DESCRIPTION
IZAMAX searches a double complex vector for the first occurrence of the
maximum absolute value.
IZAMAX determines the first index i such that
|Real(x )|+ |Imag(x ) | = MAX(|Real(x )| + | Imag(x )|): j = 1, ..., n
i i j j
where x is an element of a double complex vector.
j
ARGUMENTS
n INTEGER. (input)
Number of elements to process in the vector to be searched. If
n <= 0, these routines return 0.
x DOUBLE COMPLEX. (input)
Array of dimension (n-1) * |incx| + 1.
Array x contains the vector to be searched.
incx INTEGER. (input)
Increment between elements of x.
RETURN VALUES
IZAMAX INTEGER. (output)
Return the first index of the maximum absolute value of vector
x. The vector x has length n and increment incx.
NOTES
This routine is Level 1 Basic Linear Algebra Subprograms (Level 1
BLAS).
When working backward (incx < 0), each routine starts at the end of the
vector and moves backward, as follows:
x(1-incx * (n-1)), x(1-incx * (n-2)), ..., x(1)
The largest absolute value is:
ABS (x(1+(index-1) * incx)) when incx > 0
ABS (x(1+(n-index) * |incx|)) when incx < 0
BLAS routine IZAMAX(3)