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(in)equality comparison for double was far too tolerant

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Martin Diehl 2017-11-21 09:18:03 +01:00
parent 37e154de65
commit 09a66d918d
1 changed files with 12 additions and 8 deletions
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src/prec.f90
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@ -137,6 +137,7 @@ end subroutine prec_init
!> @brief equality comparison for float with double precision
! replaces "==" but for certain (relative) tolerance. Counterpart to dNeq
! https://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/
! AlmostEqualRelative
!--------------------------------------------------------------------------------------------------
logical elemental pure function dEq(a,b,tol)
@ -153,6 +154,7 @@ end function dEq
!> @brief inequality comparison for float with double precision
! replaces "!=" but for certain (relative) tolerance. Counterpart to dEq
! https://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/
! AlmostEqualRelative NOT
!--------------------------------------------------------------------------------------------------
logical elemental pure function dNeq(a,b,tol)
@ -167,33 +169,35 @@ end function dNeq
!--------------------------------------------------------------------------------------------------
!> @brief equality to 0 comparison for float with double precision
! replaces "==0" but for certain (absolute) tolerance. Counterpart to dNeq0
! https://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/
! replaces "==0" but everything not representable as a normal number is treated as 0. Counterpart to dNeq0
! https://de.mathworks.com/help/matlab/ref/realmin.html
! https://docs.oracle.com/cd/E19957-01/806-3568/ncg_math.html
!--------------------------------------------------------------------------------------------------
logical elemental pure function dEq0(a,tol)
implicit none
real(pReal), intent(in) :: a
real(pReal), intent(in), optional :: tol
real(pReal), parameter :: eps = 2.220446049250313E-16 ! DBL_EPSILON in C
real(pReal), parameter :: eps = 2.2250738585072014E-308 ! smallest non-denormalized number
dEq0 = merge(.True., .False.,abs(a) <= merge(tol,eps,present(tol))*10.0_pReal)
dEq0 = merge(.True., .False.,abs(a) <= merge(tol,eps,present(tol)))
end function dEq0
!--------------------------------------------------------------------------------------------------
!> @brief inequality to 0 comparison for float with double precision
! replaces "!=0" but for certain (absolute) tolerance. Counterpart to dEq0
! https://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/
! replaces "!=0" but everything not representable as a normal number is treated as 0. Counterpart to dEq0
! https://de.mathworks.com/help/matlab/ref/realmin.html
! https://docs.oracle.com/cd/E19957-01/806-3568/ncg_math.html
!--------------------------------------------------------------------------------------------------
logical elemental pure function dNeq0(a,tol)
implicit none
real(pReal), intent(in) :: a
real(pReal), intent(in), optional :: tol
real(pReal), parameter :: eps = 2.220446049250313E-16 ! DBL_EPSILON in C
real(pReal), parameter :: eps = 2.2250738585072014E-308 ! smallest non-denormalized number
dNeq0 = merge(.False., .True.,abs(a) <= merge(tol,eps,present(tol))*10.0_pReal)
dNeq0 = merge(.False., .True.,abs(a) <= merge(tol,eps,present(tol)))
end function dNeq0