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halfFunction.h
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33 ///////////////////////////////////////////////////////////////////////////
34 
35 // Primary authors:
36 // Florian Kainz <kainz@ilm.com>
37 // Rod Bogart <rgb@ilm.com>
38 
39 
40 //---------------------------------------------------------------------------
41 //
42 // halfFunction<T> -- a class for fast evaluation
43 // of half --> T functions
44 //
45 // The constructor for a halfFunction object,
46 //
47 // halfFunction (function,
48 // domainMin, domainMax,
49 // defaultValue,
50 // posInfValue, negInfValue,
51 // nanValue);
52 //
53 // evaluates the function for all finite half values in the interval
54 // [domainMin, domainMax], and stores the results in a lookup table.
55 // For finite half values that are not in [domainMin, domainMax], the
56 // constructor stores defaultValue in the table. For positive infinity,
57 // negative infinity and NANs, posInfValue, negInfValue and nanValue
58 // are stored in the table.
59 //
60 // The tabulated function can then be evaluated quickly for arbitrary
61 // half values by calling the the halfFunction object's operator()
62 // method.
63 //
64 // Example:
65 //
66 // #include <math.h>
67 // #include <halfFunction.h>
68 //
69 // halfFunction<half> hsin (sin);
70 //
71 // halfFunction<half> hsqrt (sqrt, // function
72 // 0, HALF_MAX, // domain
73 // half::qNan(), // sqrt(x) for x < 0
74 // half::posInf(), // sqrt(+inf)
75 // half::qNan(), // sqrt(-inf)
76 // half::qNan()); // sqrt(nan)
77 //
78 // half x = hsin (1);
79 // half y = hsqrt (3.5);
80 //
81 //---------------------------------------------------------------------------
82 
83 #ifndef _HALF_FUNCTION_H_
84 #define _HALF_FUNCTION_H_
85 
86 #include "half.h"
87 
88 #include "IlmBaseConfig.h"
89 #ifndef ILMBASE_HAVE_LARGE_STACK
90 #include <string.h> // need this for memset
91 #else
92 #endif
93 
94 #include <float.h>
95 
96 
97 template <class T>
99 {
100  public:
101 
102  //------------
103  // Constructor
104  //------------
105 
106  template <class Function>
107  halfFunction (Function f,
108  half domainMin = -HALF_MAX,
109  half domainMax = HALF_MAX,
110  T defaultValue = 0,
111  T posInfValue = 0,
112  T negInfValue = 0,
113  T nanValue = 0);
114 
115 #ifndef ILMBASE_HAVE_LARGE_STACK
116  ~halfFunction () { delete [] _lut; }
117 #endif
118 
119  //-----------
120  // Evaluation
121  //-----------
122 
123  T operator () (half x) const;
124 
125  private:
126 
127 #ifdef ILMBASE_HAVE_LARGE_STACK
128  T _lut[1 << 16];
129 #else
130  T * _lut;
131 #endif
132 };
133 
134 
135 //---------------
136 // Implementation
137 //---------------
138 
139 template <class T>
140 template <class Function>
142  half domainMin,
143  half domainMax,
144  T defaultValue,
145  T posInfValue,
146  T negInfValue,
147  T nanValue)
148 {
149 #ifndef ILMBASE_HAVE_LARGE_STACK
150  _lut = new T[1<<16];
151  memset (_lut, 0 , (1<<16) * sizeof(T));
152 #endif
153 
154  for (int i = 0; i < (1 << 16); i++)
155  {
156  half x;
157  x.setBits (i);
158 
159  if (x.isNan())
160  _lut[i] = nanValue;
161  else if (x.isInfinity())
162  _lut[i] = x.isNegative()? negInfValue: posInfValue;
163  else if (x < domainMin || x > domainMax)
164  _lut[i] = defaultValue;
165  else
166  _lut[i] = f (x);
167  }
168 }
169 
170 
171 template <class T>
172 inline T
174 {
175  return _lut[x.bits()];
176 }
177 
178 
179 #endif
#define HALF_MAX
Definition: half.h:267
bool isNegative() const
Definition: half.h:702
T operator()(half x) const
Definition: halfFunction.h:173
png_uint_32 i
Definition: png.h:2877
bool isInfinity() const
Definition: half.h:693
bool isNan() const
Definition: half.h:684
GLfloat f
Definition: glcorearb.h:1925
halfFunction(Function f, half domainMin=-HALF_MAX, half domainMax=HALF_MAX, T defaultValue=0, T posInfValue=0, T negInfValue=0, T nanValue=0)
Definition: halfFunction.h:141
GLint GLenum GLint x
Definition: glcorearb.h:408
void setBits(unsigned short bits)
Definition: half.h:752
unsigned short bits() const
Definition: half.h:745
Definition: half.h:91