'\" te
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.TH vatan2_ 3MVEC "14 Dec 2007" "SunOS 5.11" "Vector Math Library Functions"
.SH NAME
vatan2_, vatan2f_ \- vector atan2 functions
.SH SYNOPSIS
.LP
.nf
cc [ \fIflag\fR\&.\|.\|. ] \fIfile\fR\&.\|.\|. \fB-lmvec\fR [ \fIlibrary\fR\&.\|.\|. ]

\fBvoid\fR \fBvatan2_\fR(\fBint *\fR\fIn\fR, \fBdouble * restrict\fR \fIy\fR, \fBint *\fR\fIstridey\fR,
     \fBdouble * restrict\fR \fIx\fR, \fBint *\fR\fIstridex\fR, \fBdouble * restrict\fR \fIz\fR,
     \fBint *\fR\fIstridez\fR);
.fi

.LP
.nf
\fBvoid\fR \fBvatan2f_\fR(\fBint *\fR\fIn\fR, \fBfloat * restrict\fR \fIy\fR, \fBint *\fR\fIstridey\fR,
     \fBfloat * restrict\fR \fIx\fR, \fBint *\fR\fIstridex\fR, \fBfloat * restrict\fR \fIz\fR,
     \fBint *\fR\fIstridez\fR);
.fi

.SH DESCRIPTION
.sp
.LP
These functions evaluate the function \fBatan2\fR(\fIy\fR, \fIx\fR) 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.
.sp
.LP
Specifically, \fBvatan2_\fR(\fIn,\fR \fIy\fR, \fIsy\fR, \fIx\fR, \fIsx\fR,
\fIz\fR, \fIsz\fR) computes \fIz\fR[\fIi\fR * *\fIsz\fR] =
\fBatan2\fR(\fIy\fR[\fIi\fR * *\fIsy\fR], \fIx\fR[\fIi\fR * *\fIsx\fR]) for
each \fIi\fR = 0, 1, ..., *\fIn\fR - 1. The \fBvatan2f_()\fR  function performs
the same computation for single precision data.
.sp
.LP
These functions are not guaranteed to deliver results that are identical to the
results of the \fBatan2\fR(3M) functions given the same arguments.
Non-exceptional results, however, are accurate to within a unit in the last
place.
.SH USAGE
.sp
.LP
The element count *\fIn\fR 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.
.sp
.LP
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.
.sp
.LP
These functions handle special cases and exceptions in the same way as the
\fBatan2()\fR functions when \fBc99\fR \fBMATHERREXCEPT\fR conventions are in
effect. See \fBatan2\fR(3M) for the results for special cases.
.sp
.LP
An application wanting to check for exceptions should call
\fBfeclearexcept\fR(\fBFE_ALL_EXCEPT\fR) before calling these functions. On
return, if \fBfetestexcept\fR(\fBFE_INVALID\fR | \fBFE_DIVBYZERO\fR |
\fBFE_OVERFLOW\fR | \fBFE_UNDERFLOW\fR) 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.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
tab() box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPEATTRIBUTE VALUE
_
Interface StabilityCommitted
_
MT-LevelMT-Safe
.TE

.SH SEE ALSO
.sp
.LP
\fBatan2\fR(3M), \fBfeclearexcept\fR(3M), \fBfetestexcept\fR(3M),
\fBattributes\fR(5)