real.h File Reference

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Description

Declares real and related constants.

Macros
#define	GMX_DOUBLE_EPS   2.2204460492503131e-16
	Double precision accuracy.
#define	GMX_DOUBLE_MAX   1.7976931348623157e+308
	Maximum double precision value - reduced 1 unit in last digit for MSVC.
#define	GMX_DOUBLE_MIN   2.2250738585072014e-308
	Minimum double precision value.
#define	GMX_FLOAT_EPS   1.19209290e-07F
	Single precision accuracy.
#define	GMX_FLOAT_MAX   3.40282346E+38F
	Maximum single precision value - reduced 1 unit in last digit for MSVC.
#define	GMX_FLOAT_MIN   1.175494351E-38F
	Minimum single precision value.
#define	GMX_DOUBLE_NEGZERO   (-0.0)
	Negative zero in double.
#define	GMX_FLOAT_NEGZERO   (-0.0f)
	Negative zero in float.
#define	GMX_FLOAT_MAX_SIMD_WIDTH   16
	The maximum supported number of float elements in a SIMD register.
#define	GMX_DOUBLE_MAX_SIMD_WIDTH   8
	The maximum supported number of double elements in a SIMD register.
#define	HAVE_REAL
	Used to check whether real is already defined.
#define	GMX_MPI_REAL   MPI_FLOAT
	MPI data type for real.
#define	GMX_REAL_EPS   GMX_FLOAT_EPS
	Accuracy for real.
#define	GMX_REAL_MIN   GMX_FLOAT_MIN
	Smallest non-zero value for real.
#define	GMX_REAL_MAX   GMX_FLOAT_MAX
	Largest finite value for real.
#define	GMX_REAL_NEGZERO   GMX_FLOAT_NEGZERO
	Negative zero for real.
#define	gmx_real_fullprecision_pfmt   "%14.7e"
	Format string for full real precision.
#define	GMX_REAL_MAX_SIMD_WIDTH   GMX_FLOAT_MAX_SIMD_WIDTH
	The maximum supported number of real elements in a SIMD register.

Typedefs
typedef float	real
	Precision-dependent GROMACS floating-point type.

Functions
constexpr real	operator""_real (long double x)
	User defined literal for real numbers. More...

Function Documentation

constexpr real operator""_real

(

long double

x

)

User defined literal for real numbers.

Examples: 2._real, 2.5_real, .5_real. The number is always of type real.

It is best to use a real constant whenever it is used only with operands which are real. If a constant is double than the compiler is forced to do operations directly involving the constant in double even if all variables are real. A constant shouldn't be real when used with double operands, because then the constant is less accurate with GMX_DOUBLE=no.

See https://en.cppreference.com/w/cpp/language/user_literal for details on this lanuage feature.