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Vector Math Library Functions                      vatan2_(3MVEC)



NAME
     vatan2_, vatan2f_ - vector atan2 functions

SYNOPSIS
     cc [ flag... ] file... -lmvec [ library... ]

     void vatan2_(int *n, double * restrict y, int *stridey,
          double * restrict x, int *stridex, double * restrict z,
          int *stridez);


     void vatan2f_(int *n, float * restrict y, int *stridey,
          float * restrict x, int *stridex, float * restrict z,
          int *stridez);


DESCRIPTION
     These functions evaluate the function  atan2(y,  x)  for  an
     entire  vector of values at once. The first parameter speci-
     fies the number of values to compute. Subsequent  parameters
     specify  the  argument  and  result  vectors. Each vector is
     described by a pointer to the first element  and  a  stride,
     which is the increment between successive elements.


     Specifically, vatan2_(n, y, sy, x, sx, z, sz) computes z[i *
     *sz] = atan2(y[i * *sy], x[i * *sx]) for each i = 0, 1, ...,
     *n - 1. The vatan2f_()  function performs the same  computa-
     tion for single precision data.


     These functions are not guaranteed to deliver  results  that
     are  identical  to  the  results  of the atan2(3M) functions
     given the same arguments. Non-exceptional results,  however,
     are accurate to within a unit in the last place.

USAGE
     The element count *n must be greater than zero. The  strides
     for   the  argument  and  result  arrays  can  be  arbitrary
     integers, but the arrays themselves must not be the same  or
     overlap.  A zero stride effectively collapses an entire vec-
     tor into a single element. A negative stride causes a vector
     to be accessed in descending memory order, but note that the
     corresponding pointer must still point to the first  element
     of  the  vector  to be used; if the stride is negative, this
     will be the highest-addressed element in memory.  This  con-
     vention differs from the Level 1 BLAS, in which array param-
     eters always refer to the lowest-addressed element in memory
     even when negative increments are used.






SunOS 5.11          Last change: 14 Dec 2007                    1






Vector Math Library Functions                      vatan2_(3MVEC)



     These functions assume  that  the  default  round-to-nearest
     rounding  direction  mode  is in effect. On x86, these func-
     tions also assume that the default round-to-64-bit  rounding
     precision  mode is in effect. The result of calling a vector
     function with a non-default rounding mode in effect is unde-
     fined.


     These functions handle special cases and exceptions  in  the
     same  way  as  the  atan2() functions when c99 MATHERREXCEPT
     conventions are in effect. See atan2(3M) for the results for
     special cases.


     An application wanting to check for exceptions  should  call
     feclearexcept(FE_ALL_EXCEPT) before calling these functions.
     On  return,  if  fetestexcept(FE_INVALID  |  FE_DIVBYZERO  |
     FE_OVERFLOW  |  FE_UNDERFLOW)  is non-zero, an exception has
     been raised. The application can then examine the result  or
     argument  vectors  for exceptional values. Some vector func-
     tions can raise the inexact exception even if  all  elements
     of  the  argument  array are such that the numerical results
     are exact.

ATTRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:



     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Interface Stability         | Committed                   |
    |_____________________________|_____________________________|
    | MT-Level                    | MT-Safe                     |
    |_____________________________|_____________________________|


SEE ALSO
     atan2(3M),   feclearexcept(3M),   fetestexcept(3M),   attri-
     butes(5)













SunOS 5.11          Last change: 14 Dec 2007                    2