Vector Math Library Functions vrhypot(3MVEC)
NAME
vrhypot, vrhypotf - vector reciprocal hypotenuse functions
SYNOPSIS
cc [ flag... ] file... -lmvec [ library... ]
void vrhypot(int *n, double * restrict x, int *stridex,
double * restrict y, int *stridey, double * restrict z,
int *stridez);
void vrhypotf(int *n, float * restrict x, int *stridex,
float * restrict y, int *stridey, float * restrict z,
int *stridez);
DESCRIPTION
These functions evaluate the function rhypot(x, y), defined
by rhypot(x, y) = 1 / hypot(x, y), for an entire vector of
values at once. The first parameter specifies the number of
values to compute. Subsequent parameters specify the argu-
ment 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, vrhypot(n, x, sx, y, sy, z, sz) computes z[i
* *sz] = rhypot(x[i * *sx], y[i * *sy]) for each i = 0, 1,
..., *n - 1. The vrhypotf() function performs the same
computation for single precision data.
These functions are not guaranteed to deliver results that
are identical to the results of evaluating 1.0 / hypot(x, y)
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 vrhypot(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
spirit of IE 754. In particular,
o if x or y is ]Inf, rhypot(x, y) is ]0, even if the
other of x or y is NaN,
o if x or y is NaN and neither is infinite, rhypot(x,
y) is NaN
o if x and y are both zero, rhypot(x, y) is ]0, and a
division-by-zero exception is raised.
An application wanting to check for exceptions should call
feclearexcept(FEALEXCEPT) before calling these functions.
On return, if fetestexcept(FEINVALID FEDIVBYZERO
FEOVERFLOW FEUNDERFLOW) 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.
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
ATRIBUTE TYPE ATRIBUTE VALUE
Interface Stability Committed
MT-Level MT-Safe
SEE ALSO
hypot(3M), feclearexcept(3M), fetestexcept(3M), attri-
butes(5)
SunOS 5.11 Last change: 14 Dec 2007 2
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