samax, damax, scamax, dzamax 

Maximum absolute value

FORMAT

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

Function Value

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

Arguments

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

  x                   real*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.

  incx                integer*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.