Generate and return .true. if the input value is an IEEE-compliant NAN (Not a Number) or if the input value x is not equal to its input copy xcopy, a characteristic behavior of NAN values.
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Detailed Description

Generate and return .true. if the input value is an IEEE-compliant NAN (Not a Number) or if the input value x is not equal to its input copy xcopy, a characteristic behavior of NAN values.

If the input value is a complex number, then the output is .true. if any of the real or imaginary components or both components are NaN.

Parameters

[in]	x	: The input scalar or array of the same rank as other input array-like arguments of either type `complex` of kind any supported by the processor (e.g., CK, CK32, CK64, or CK128), or type `real` of kind any supported by the processor (e.g., RK, RK32, RK64, or RK128), whose value will be tested for being `NaN`.
[in]	xcopy	: The input scalar or array of the same rank as other input array-like arguments, of the same type and kind and value as the input argument `x`. When `xcopy` is missing, the procedure relies on IEEE-compliant intrinsic routines for detecting `NaN`. When `xcopy` is present, its value is directly compared with the input `x` for non-equality to detect `NaN`. (optional. If missing, IEEE-compliance is assumed for detecting `NaN`.)

Returns: isNotANumber : The output scalar or array of the same shape as the input x of type logical of default kind LK whose value is .true. if the input x is NaN, otherwise it is .false..

Possible calling interfaces ⛓

: use pm_kind, only: LK

use pm_except, only: isNAN

logical(LK) :: isNotANumber

isNotANumber = isNAN(x)

isNotANumber = isNAN(x, xcopy)

pm_except::isNAN
Generate and return .true. if the input value is an IEEE-compliant NAN (Not a Number) or if the input...
Definition: pm_except.F90:2103

pm_except
This module contains procedures and generic interfaces for testing for exceptional cases at runtime.
Definition: pm_except.F90:46

pm_kind
This module defines the relevant Fortran kind type-parameters frequently used in the ParaMonte librar...
Definition: pm_kind.F90:268

pm_kind::LK
integer, parameter LK
The default logical kind in the ParaMonte library: kind(.true.) in Fortran, kind(....
Definition: pm_kind.F90:541

Warning: Keep in mind that NaN might not even be defined for non-IEEE-compliant compilers or when certain aggressive IEEE-breaking optimization flags are specified like -O3 -ffast-math with GNU gfortran or -fast with Intel ifort compilers.
In such cases, this algorithm with only one input argument which relies on IEEE-compliance may spectacularly fail.
After all, why would one need NaN in fast mode?
The two-arguments interface relies on the observation that NaN is the only value that is not equal to itself.
This approach to detecting NaN works as long as the compiler does not perform aggressive optimizations to inline the NaN-detection procedure, thereby allowing to eliminate the direct comparison of x with itself through aggressive optimizations.
As such, the procedures under the two-arguments interface are declared impure to present inlining of the procedures.

Remarks: The procedures of this generic interface are pure with one input argument and impure with two input arguments.; The procedures under discussion are elemental.

Note: According to the IEEE definition, if a real variable x is NaN then x /= x always yields .true..
This can be simple fast test of NaN when the processor is IEEE-compliant.
However, keep in mind that some compilers might optimize such comparison away.; The procedures under this generic interface with single input argument x use ieee_is_nan(x) from the ieee_arithmetic intrinsic module to detect NaN values.
This generic interface extends this function also to complex numbers.; Note that the Intel and GNU Fortran compilers also have the isnan(x) extension function.

See also: isInf
isNAN
getNAN
setNAN
isInfPos
isInfNeg
getInfPos
setInfPos
getInfNeg
setInfNeg

Example usage ⛓

: 1program example

2

3 use pm_kind, only: SK, IK

4 use pm_kind, only: RKS, RKD, RKH ! all processor types and kinds are supported.

5 use pm_kind, only: CKS, CKD, CKH ! all processor types and kinds are supported.

6 use pm_io, only: display_type

7 use pm_except, only: isNAN, setNAN

8

9 implicit none

10

11 real(RKH) :: X_RKH(3)

12 real(RKD) :: X_RKD(3)

13 real(RKS) :: X_RKS(3)

14 complex(CKH) :: X_CKH(3)

15 complex(CKD) :: X_CKD(3)

16 complex(CKS) :: X_CKS(3)

17

18 type(display_type) :: disp

19 disp = display_type(file = "main.out.F90")

20

21 call setNAN(X_RKH)

22 call setNAN(X_RKD)

23 call setNAN(X_RKS)

24

25 call setNAN(X_CKH)

26 call setNAN(X_CKD)

27 call setNAN(X_CKS)

28

29 X_RKH(2) = 0._RKH

30 X_RKD(2) = 0._RKD

31 X_RKS(2) = 0._RKS

32

33 X_CKH(2) = (0._CKH, 0._CKH)

34 X_CKD(2) = (0._CKD, 0._CKD)

35 X_CKS(2) = (0._CKS, 0._CKS)

36

37 X_CKH(2) = cmplx(0._CKH, X_RKH(1), CKH)

38 X_CKD(2) = cmplx(X_RKD(1), 0._CKD, CKD)

39 X_CKS(2) = cmplx(0._CKS, 0._CKS, CKS)

40

41 call disp%skip

42 call disp%show("!%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%")

43 call disp%show("!%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%")

44 call disp%show("!Generate real IEEE-compliant NaN.")

45 call disp%show("!%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%")

46 call disp%show("!%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%")

47 call disp%skip

48

49 call disp%skip

50 call disp%show("!%%%%%%%%%%%")

51 call disp%show("!32-bit real")

52 call disp%show("!%%%%%%%%%%%")

53 call disp%skip

54

55 call disp%skip

56 call disp%show("X_RKS(1)")

57 call disp%show( X_RKS(1) )

58 call disp%show("isNAN(X_RKS(1))")

59 call disp%show( isNAN(X_RKS(1)) )

60 call disp%skip

61

62 call disp%skip

63 call disp%show("X_RKS")

64 call disp%show( X_RKS )

65 call disp%show("isNAN(X_RKS)")

66 call disp%show( isNAN(X_RKS) )

67 call disp%skip

68

69 call disp%skip

70 call disp%show("!%%%%%%%%%%%")

71 call disp%show("!64-bit real")

72 call disp%show("!%%%%%%%%%%%")

73 call disp%skip

74

75 call disp%skip

76 call disp%show("X_RKD(1)")

77 call disp%show( X_RKD(1) )

78 call disp%show("isNAN(X_RKD(1))")

79 call disp%show( isNAN(X_RKD(1)) )

80 call disp%skip

81

82 call disp%skip

83 call disp%show("X_RKD")

84 call disp%show( X_RKD)

85 call disp%show("isNAN(X_RKD)")

86 call disp%show( isNAN(X_RKD) )

87 call disp%skip

88

89 call disp%skip

90 call disp%show("!%%%%%%%%%%%%")

91 call disp%show("!128-bit real")

92 call disp%show("!%%%%%%%%%%%%")

93 call disp%skip

94

95 call disp%skip

96 call disp%show("X_RKH(1)")

97 call disp%show( X_RKH(1) )

98 call disp%show("isNAN(X_RKH(1))")

99 call disp%show( isNAN(X_RKH(1)) )

100 call disp%skip

101

102 call disp%skip

103 call disp%show("X_RKH")

104 call disp%show( X_RKH )

105 call disp%show("isNAN(X_RKH)")

106 call disp%show( isNAN(X_RKH) )

107 call disp%skip

108

109

110 call disp%skip

111 call disp%show("!%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%")

112 call disp%show("!%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%")

113 call disp%show("!Generate complex IEEE-compliant NaN.")

114 call disp%show("!%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%")

115 call disp%show("!%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%")

116 call disp%skip

117

118

119 call disp%skip

120 call disp%show("!%%%%%%%%%%%%%%")

121 call disp%show("!32-bit complex")

122 call disp%show("!%%%%%%%%%%%%%%")

123 call disp%skip

124

125 call disp%skip

126 call disp%show("X_CKS(1)")

127 call disp%show( X_CKS(1) )

128 call disp%show("isNAN(X_CKS(1))")

129 call disp%show( isNAN(X_CKS(1)) )

130 call disp%skip

131

132 call disp%skip

133 call disp%show("X_CKS")

134 call disp%show( X_CKS )

135 call disp%show("isNAN(X_CKS)")

136 call disp%show( isNAN(X_CKS) )

137 call disp%skip

138

139 call disp%skip

140 call disp%show("!%%%%%%%%%%%%%%")

141 call disp%show("!64-bit complex")

142 call disp%show("!%%%%%%%%%%%%%%")

143 call disp%skip

144

145 call disp%skip

146 call disp%show("X_CKD(1)")

147 call disp%show( X_CKD(1) )

148 call disp%show("isNAN(X_CKD(1))")

149 call disp%show( isNAN(X_CKD(1)) )

150 call disp%skip

151

152 call disp%skip

153 call disp%show("X_CKD")

154 call disp%show( X_CKD )

155 call disp%show("isNAN(X_CKD)")

156 call disp%show( isNAN(X_CKD) )

157 call disp%skip

158

159 call disp%skip

160 call disp%show("!%%%%%%%%%%%%%%%")

161 call disp%show("!128-bit complex")

162 call disp%show("!%%%%%%%%%%%%%%%")

163 call disp%skip

164

165 call disp%skip

166 call disp%show("X_CKH(1)")

167 call disp%show( X_CKH(1) )

168 call disp%show("isNAN(X_CKH(1))")

169 call disp%show( isNAN(X_CKH(1)) )

170 call disp%skip

171

172 call disp%skip

173 call disp%show("X_CKH")

174 call disp%show( X_CKH )

175 call disp%show("isNAN(X_CKH)")

176 call disp%show( isNAN(X_CKH) )

177 call disp%skip

178

179end program example

pm_except::setNAN
Return an IEEE-compliant quiet NAN (Not a Number).
Definition: pm_except.F90:2593

pm_io::show
This is a generic method of the derived type display_type with pass attribute.
Definition: pm_io.F90:11726

pm_io::skip
This is a generic method of the derived type display_type with pass attribute.
Definition: pm_io.F90:11508

pm_io
This module contains classes and procedures for input/output (IO) or generic display operations on st...
Definition: pm_io.F90:252

pm_io::disp
type(display_type) disp
This is a scalar module variable an object of type display_type for general display.
Definition: pm_io.F90:11393

pm_kind::CKH
integer, parameter CKH
The scalar integer constant of intrinsic default kind, representing the highest-precision complex kin...
Definition: pm_kind.F90:843

pm_kind::CKS
integer, parameter CKS
The single-precision complex kind in Fortran mode. On most platforms, this is a 32-bit real kind.
Definition: pm_kind.F90:570

pm_kind::IK
integer, parameter IK
The default integer kind in the ParaMonte library: int32 in Fortran, c_int32_t in C-Fortran Interoper...
Definition: pm_kind.F90:540

pm_kind::CKD
integer, parameter CKD
The double precision complex kind in Fortran mode. On most platforms, this is a 64-bit real kind.
Definition: pm_kind.F90:571

pm_kind::RKD
integer, parameter RKD
The double precision real kind in Fortran mode. On most platforms, this is an 64-bit real kind.
Definition: pm_kind.F90:568

pm_kind::SK
integer, parameter SK
The default character kind in the ParaMonte library: kind("a") in Fortran, c_char in C-Fortran Intero...
Definition: pm_kind.F90:539

pm_kind::RKH
integer, parameter RKH
The scalar integer constant of intrinsic default kind, representing the highest-precision real kind t...
Definition: pm_kind.F90:858

pm_kind::RKS
integer, parameter RKS
The single-precision real kind in Fortran mode. On most platforms, this is an 32-bit real kind.
Definition: pm_kind.F90:567

pm_io::display_type
Generate and return an object of type display_type.
Definition: pm_io.F90:10282

Example Unix compile command via Intel ifort compiler ⛓
1#!/usr/bin/env sh

2rm main.exe

3ifort -fpp -standard-semantics -O3 -Wl,-rpath,../../../lib -I../../../inc main.F90 ../../../lib/libparamonte* -o main.exe

4./main.exe

Example Windows Batch compile command via Intel ifort compiler ⛓
1del main.exe

2set PATH=..\..\..\lib;%PATH%

3ifort /fpp /standard-semantics /O3 /I:..\..\..\include main.F90 ..\..\..\lib\libparamonte*.lib /exe:main.exe

4main.exe

Example Unix / MinGW compile command via GNU gfortran compiler ⛓
1#!/usr/bin/env sh

2rm main.exe

3gfortran -cpp -ffree-line-length-none -O3 -Wl,-rpath,../../../lib -I../../../inc main.F90 ../../../lib/libparamonte* -o main.exe

4./main.exe

Example output ⛓
1

2!%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

3!%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

4!Generate real IEEE-compliant NaN.

5!%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

6!%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

7

8

9!%%%%%%%%%%%

10!32-bit real

11!%%%%%%%%%%%

12

13

14X_RKS(1)

15NaN

16isNAN(X_RKS(1))

17T

18

19

20X_RKS

21NaN, +0.00000000, NaN

22isNAN(X_RKS)

23T, F, T

24

25

26!%%%%%%%%%%%

27!64-bit real

28!%%%%%%%%%%%

29

30

31X_RKD(1)

32NaN

33isNAN(X_RKD(1))

34T

35

36

37X_RKD

38NaN, +0.0000000000000000, NaN

39isNAN(X_RKD)

40T, F, T

41

42

43!%%%%%%%%%%%%

44!128-bit real

45!%%%%%%%%%%%%

46

47

48X_RKH(1)

49NaN

50isNAN(X_RKH(1))

51T

52

53

54X_RKH

55NaN, +0.00000000000000000000000000000000000, NaN

56isNAN(X_RKH)

57T, F, T

58

59

60!%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

61!%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

62!Generate complex IEEE-compliant NaN.

63!%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

64!%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

65

66

67!%%%%%%%%%%%%%%

68!32-bit complex

69!%%%%%%%%%%%%%%

70

71

72X_CKS(1)

73(NaN, NaN)

74isNAN(X_CKS(1))

75T

76

77

78X_CKS

79(NaN, NaN), (+0.00000000, +0.00000000), (NaN, NaN)

80isNAN(X_CKS)

81T, F, T

82

83

84!%%%%%%%%%%%%%%

85!64-bit complex

86!%%%%%%%%%%%%%%

87

88

89X_CKD(1)

90(NaN, NaN)

91isNAN(X_CKD(1))

92T

93

94

95X_CKD

96(NaN, NaN), (NaN, +0.0000000000000000), (NaN, NaN)

97isNAN(X_CKD)

98T, T, T

99

100

101!%%%%%%%%%%%%%%%

102!128-bit complex

103!%%%%%%%%%%%%%%%

104

105

106X_CKH(1)

107(NaN, NaN)

108isNAN(X_CKH(1))

109T

110

111

112X_CKH

113(NaN, NaN), (+0.00000000000000000000000000000000000, NaN), (NaN, NaN)

114isNAN(X_CKH)

115T, T, T

116

117

Test:: test_pm_except

Todo:: Critical Priority: The implementation of the test for NaN should be improved to a bitwise comparison that is also valid with non-IEEE-compliant processors.

Final Remarks ⛓

If you believe this algorithm or its documentation can be improved, we appreciate your contribution and help to edit this page's documentation and source file on GitHub.
For details on the naming abbreviations, see this page.
For details on the naming conventions, see this page.
This software is distributed under the MIT license with additional terms outlined below.

If you use any parts or concepts from this library to any extent, please acknowledge the usage by citing the relevant publications of the ParaMonte library.
If you regenerate any parts/ideas from this library in a programming environment other than those currently supported by this ParaMonte library (i.e., other than C, C++, Fortran, MATLAB, Python, R), please also ask the end users to cite this original ParaMonte library.

This software is available to the public under a highly permissive license.
Help us justify its continued development and maintenance by acknowledging its benefit to society, distributing it, and contributing to it.

Copyright: Computational Data Science Lab

Author:: Amir Shahmoradi, Friday 1:54 AM, April 21, 2017, Institute for Computational Engineering and Sciences (ICES), The University of Texas, Austin, TX

Definition at line 2103 of file pm_except.F90.

The documentation for this interface was generated from the following file:

src/fortran/main/pm_except.F90