VATAN2_(3MVEC) Vector Math Library Functions VATAN2_(3MVEC)


vatan2_, vatan2f_ - vector atan2 functions


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);


These functions evaluate the function atan2(y, x) for an entire vector of
values at once. The first parameter specifies 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 computation for single precision

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


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 vector 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 convention differs from the Level 1
BLAS, in which array parameters always refer to the lowest-addressed
element in memory even when negative increments are used.

These functions assume that the default round-to-nearest rounding
direction mode is in effect. On x86, these functions 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 undefined.

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,
is non-zero, an exception has been raised. The application can then
examine the result or argument vectors for exceptional values. Some
vector functions can raise the inexact exception even if all elements of
the argument array are such that the numerical results are exact.


See attributes(5) for descriptions of the following attributes:

|Interface Stability | Committed |
|MT-Level | MT-Safe |


atan2(3M), feclearexcept(3M), fetestexcept(3M), attributes(5)

SunOS 5.11 December 14, 2007 VATAN2_(3MVEC)