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

NAME

vatan_, vatanf_ - vector arctangent functions

SYNOPSIS

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

void vatan_(int *n,double * restrict x, int *stridex,
double * restrict y, int *stridey);


void vatanf_(int *n, float * restrict x, int *stridex,
float * restrict y, int *stridey);

DESCRIPTION

These functions evaluate the function atan(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, vatan_(n, x, sx, y, sy) computes y[i * *sy] = atan(x[i
* *sx]) for each i = 0, 1, ..., *n - 1. The vatanf_() function
performs the same computation for single precision data.


These functions are not guaranteed to deliver results that are
identical to the results of the atan(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 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 atan() functions when c99 MATHERREXCEPT conventions are in
effect. See atan(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 functions can raise the inexact
exception even if all elements of the argument array are such that
the numerical results are exact.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+----------------------------+-----------------------------+
|Interface Stability | Committed |
+----------------------------+-----------------------------+
|MT-Level | MT-Safe |
+----------------------------+-----------------------------+

SEE ALSO

atan(3M), feclearexcept(3M), fetestexcept(3M), attributes(7)

SunOS 5.11 December 14, 2007 VATAN_(3MVEC)