Name

samax, damax, scamax, dzamax − Maximum absolute value

FORMAT

{S,D}AMAX (n, x, incx) SCAMAX (n, x, incx) DZAMAX (n, x, incx)

Function Value

amaxreal∗4 |  real∗8
The element of the vector with the largest absolute value. If n<=0, amax returns the value 0.0. 

Arguments

ninteger∗4
On entry, the number of elements in the vector x.
On exit, n is unchanged. 

xreal∗4 |  real∗8 |  complex∗8 |  complex∗16
On entry, a one-dimensional array X of length at least (1+(n-1)∗|incx|), containing the elements of the vector x.
On exit, x is unchanged. 

incxinteger∗4
On entry, the increment for the array X.
If incx > 0, vector x is stored forward in the array, so that x(i) is stored in location X(1+(i-1)∗incx). 
If incx < 0, vector x is stored backward in the array, so that x(i) is stored in location X(1+(n-i)∗|incx|). 
If incx = 0, only the first element is accessed. 
On exit, incx is unchanged. 

Description

These functions determine the largest absolute value of the elements of a vector: MAX{|x(j)|, j = 1,2, ...,n}

For complex vectors, each element is a complex number. In this subprogram, the absolute value of a complex number is defined  as the absolute value of the real part of the complex number plus the absolute value  of the imaginary part of the complex number: |x(j)| = |a(j)| + |b(j)| = |(real)| + |(imaginary)|

If incx < 0, the result is identical to using |incx|.  If incx = 0, the computation is a time-consuming way of setting amax = |x(1)|. 

Example

INTEGER∗4 N, INCX
COMPLEX∗8 X(40), AMAX
INCX = 2
N = 20
AMAX = SCAMAX(N,X,INCX)

This FORTRAN example shows how to compute the element with the largest absolute value.