VMS Help RTL Routines, MTH$, BLAS1$VIxAMAX  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    The Obtain the Index of the First Element of a Vector Having
    the Largest Absolute Value routine finds the index of the first
    occurrence of a vector element having the maximum absolute value.

    Format

      BLAS1$VISAMAX  n ,x ,incx

      BLAS1$VIDAMAX  n ,x ,incx

      BLAS1$VIGAMAX  n ,x ,incx

      BLAS1$VICAMAX  n ,x ,incx

      BLAS1$VIZAMAX  n ,x ,incx

      BLAS1$VIWAMAX  n ,x ,incx

      Use BLAS1$VISAMAX for single-precision real operations.
      Use BLAS1$VIDAMAX for double-precision real (D-floating)
      operations.
      Use BLAS1$VIGAMAX for double-precision real (G-floating)
      operations.

      Use BLAS1$VICAMAX for single-precision complex operations.
      Use BLAS1$VIZAMAX for double-precision complex (D-floating)
      operations.
      Use BLAS1$VIWAMAX for double-precision complex (G-floating)
      operations.

1 - Returns

    OpenVMS usage:longword_signed
    type:         longword integer (signed)
    access:       write only
    mechanism:    by value

    For the real versions of this routine, the function value is
    the index of the first occurrence of a vector element having the
    maximum absolute value, as follows:

                   |xi | = ma{ |j | for j = 1,2,...,n}
                             {                       }

    |x[i]| = max{|x[j]| for j = 1,2,...,n}

    For the complex versions of this routine, the function value
    is the index of the first occurrence of a vector element having
    the largest sum of the absolute values of the real and imaginary
    parts of the vector elements, as follows:

     |Re(xi )|+|Im(xi )| = ma{ |Re(j )|+|Im(xj)| for j = 1,2,...,n }
                             {                                     }

    |Re(x[i])|  +  |Im(x[i])|   =
    max{|Re(x[j])|+|Im(x[j])|  for j = 1,2,...,n}

2 - Arguments

 n

    OpenVMS usage:longword_signed
    type:         longword integer (signed)
    access:       read only
    mechanism:    by reference

    Number of elements in vector x. The n argument is the address of
    a signed longword integer containing the number of elements. If
    you specify a negative value or 0 for n, 0 is returned.

 x

    OpenVMS usage:floating_point or complex_number
    type:         F_floating, D_floating, G_floating real or
                  F_floating, D_floating, G_floating complex
    access:       read only
    mechanism:    by reference, array reference

    Array containing the elements to be accessed. All elements of
    array x are accessed only if the increment argument of x, called
    incx, is 1. The x argument is the address of a floating-point or
    floating-point complex number that is this array. This argument
    is an array of length at least:

    1+(n-1)*|incx|

    where:

    n   =  number of vector elements specified in n
    incx=  increment argument for the array x specified in incx

    Specify the data type as follows:

    Routine            Data Type for x

    BLAS1$VISAMAX      F-floating real
    BLAS1$VIDAMAX      D-floating real
    BLAS1$VIGAMAX      G-floating real
    BLAS1$VICAMAX      F-floating complex
    BLAS1$VIZAMAX      D-floating complex
    BLAS1$VIWAMAX      G-floating complex

    If n is less than or equal to 0, then imax is 0.

 incx

    OpenVMS usage:longword_signed
    type:         longword integer (signed)
    access:       read only
    mechanism:    by reference

    Increment argument for the array x. The incx argument is the
    address of a signed longword integer containing the increment
    argument. If incx is greater than or equal to 0, then x is
    referenced forward in array x; that is, xi is referenced as:

    x(1+(i-1)*incx)

    where:

    x   =  array specified in x
    i   =  element of the vector x
    incx=  increment argument for the array x specified in incx

    If you specify a negative value for incx, it is interpreted as
    the absolute value of incx.