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   6 .TH vrhypot_ 3MVEC "14 Dec 2007" "SunOS 5.11" "Vector Math Library Functions"
   7 .SH NAME
   8 vrhypot_, vrhypotf_ \- vector reciprocal hypotenuse functions
   9 .SH SYNOPSIS
  10 .LP
  11 .nf
  12 cc [ \fIflag\fR\&.\|.\|. ] \fIfile\fR\&.\|.\|. \fB-lmvec\fR [ \fIlibrary\fR\&.\|.\|. ]
  13 
  14 \fBvoid\fR \fBvrhypot_\fR(\fBint *\fR\fIn\fR, \fBdouble * restrict\fR \fIx\fR, \fBint *\fR\fIstridex\fR,
  15      \fBdouble * restrict\fR \fIy\fR, \fBint *\fR\fIstridey\fR, \fBdouble * restrict\fR \fIz\fR,
  16      \fBint *\fR\fIstridez\fR);
  17 .fi
  18 
  19 .LP
  20 .nf
  21 \fBvoid\fR \fBvrhypotf_\fR(\fBint *\fR\fIn\fR, \fBfloat * restrict\fR \fIx\fR, \fBint *\fR\fIstridex\fR,
  22      \fBfloat * restrict\fR \fIy\fR, \fBint *\fR\fIstridey\fR, \fBfloat * restrict\fR \fIz\fR,
  23      \fBint *\fR\fIstridez\fR);
  24 .fi
  25 
  26 .SH DESCRIPTION
  27 .sp
  28 .LP
  29 These functions evaluate the function \fBrhypot\fR(\fIx\fR, \fIy\fR), defined
  30 by \fBrhypot\fR(\fIx\fR, \fIy\fR) = 1 / \fBhypot\fR(\fIx\fR, \fIy\fR), for an
  31 entire vector of values at once. The first parameter specifies the number of
  32 values to compute. Subsequent parameters specify the argument and result
  33 vectors. Each vector is described by a pointer to the first element and a
  34 stride, which is the increment between successive elements.
  35 .sp
  36 .LP
  37 Specifically, \fBvrhypot_\fR(\fIn\fR, \fIx\fR, \fIsx\fR, \fIy\fR, \fIsy\fR,
  38 \fIz\fR, \fIsz\fR) computes \fIz\fR[\fIi\fR * *\fIsz\fR] =
  39 \fBrhypot\fR(\fIx\fR[\fIi\fR * *\fIsx\fR], \fIy\fR[\fIi\fR * *\fIsy\fR]) for
  40 each \fIi\fR = 0, 1, ..., *\fIn\fR - 1. The \fBvrhypotf_()\fR  function
  41 performs the same computation for single precision data.
  42 .sp
  43 .LP
  44 These functions are not guaranteed to deliver results that are identical to the
  45 results of evaluating 1.0 / \fBhypot\fR(\fIx\fR, \fIy\fR) given the same
  46 arguments. Non-exceptional results, however, are accurate to within a unit in
  47 the last place.
  48 .SH USAGE
  49 .sp
  50 .LP
  51 The element count *\fIn\fR must be greater than zero. The strides for the
  52 argument and result arrays can be arbitrary integers, but the arrays themselves
  53 must not be the same or overlap. A zero stride effectively collapses an entire
  54 vector into a single element. A negative stride causes a vector to be accessed
  55 in descending memory order, but note that the corresponding pointer must still
  56 point to the first element of the vector to be used; if the stride is negative,
  57 this will be the highest-addressed element in memory. This convention differs
  58 from the Level 1 BLAS, in which array parameters always refer to the
  59 lowest-addressed element in memory even when negative increments are used.
  60 .sp
  61 .LP
  62 These functions assume that the default round-to-nearest rounding direction
  63 mode is in effect. On x86, these functions also assume that the default
  64 round-to-64-bit rounding precision mode is in effect. The result of calling a
  65 vector function with a non-default rounding mode in effect is undefined.
  66 .sp
  67 .LP
  68 These functions handle special cases and exceptions in the spirit of IEEE 754.
  69 In particular,
  70 .RS +4
  71 .TP
  72 .ie t \(bu
  73 .el o
  74 if x or \fIy\fR is \(+-Inf, \fBrhypot\fR(\fIx\fR, \fIy\fR) is +0, even if the
  75 other of \fIx\fR or \fIy\fR is NaN,
  76 .RE
  77 .RS +4
  78 .TP
  79 .ie t \(bu
  80 .el o
  81 if x or \fIy\fR is NaN and neither is infinite, \fBrhypot\fR(\fIx\fR, \fIy\fR)
  82 is NaN
  83 .RE
  84 .RS +4
  85 .TP
  86 .ie t \(bu
  87 .el o
  88 if \fIx\fR and \fIy\fR are both zero, \fBrhypot\fR(\fIx\fR, \fIy\fR) is +0, and
  89 a division-by-zero exception is raised.
  90 .RE
  91 .sp
  92 .LP
  93 An application wanting to check for exceptions should call
  94 \fBfeclearexcept\fR(\fBFE_ALL_EXCEPT\fR) before calling these functions. On
  95 return, if \fBfetestexcept\fR(\fBFE_INVALID\fR | \fBFE_DIVBYZERO\fR |
  96 \fBFE_OVERFLOW\fR | \fBFE_UNDERFLOW\fR) is non-zero, an exception has been
  97 raised. The application can then examine the result or argument vectors for
  98 exceptional values. Some vector functions can raise the inexact exception even
  99 if all elements of the argument array are such that the numerical results are
 100 exact.
 101 .SH ATTRIBUTES
 102 .sp
 103 .LP
 104 See \fBattributes\fR(5) for descriptions of the following attributes:
 105 .sp
 106 
 107 .sp
 108 .TS
 109 tab() box;
 110 cw(2.75i) |cw(2.75i) 
 111 lw(2.75i) |lw(2.75i) 
 112 .
 113 ATTRIBUTE TYPEATTRIBUTE VALUE
 114 _
 115 Interface StabilityCommitted
 116 _
 117 MT-LevelMT-Safe
 118 .TE
 119 
 120 .SH SEE ALSO
 121 .sp
 122 .LP
 123 \fBhypot\fR(3M), \fBfeclearexcept\fR(3M), \fBfetestexcept\fR(3M),
 124 \fBattributes\fR(5)