healpix_types

This module defines a set of parameters used by most other HEALPix modules.

Location in HEALPix directory tree: src/f90/mod/healpix_types.F90 

The parameters defined in healpix_types include

• 'kind' parameters, used when defining the type of a variable,

  name	type	value1	definition
  I1B	integer	1	number of bytes in the hardware-supported signed integers covering the range -99 to 99 with the least margin
  I2B	integer	2	same as above for the range -9999 to 9999 (ie, 4 digits)
  I4B	integer	4	same as above for 9 digits
  I8B	integer	8	same as above for 16 digits2
  SP	integer	4	number of bytes in the hardware-supported floating-point numbers covering the range $10^{-30}$ to $10^{30}$ with the least margin (hereafter single precision)
  DP	integer	8	same as above for the range $10^{-200}$ to $10^{200}$ (double precision)
  SPC	integer	4	number of bytes in real (or imaginary) part of single precision complex numbers
  DPC	integer	8	same as above for double precision complex numbers
  LGT	integer	4	number of bytes in logical variables

  ¹ actual value may depend on hardware or compiler

  ² may not be supported by some hardware or compiler; on those systems, the user should set the preprocessing variable NO64BITS to 1 during compilation to demote automatically I8B to I4B

• largest accessible numbers,

  name	type or kind	value1	definition
  MAX_I1B	integer	127	largest number accessible to integers of kind I1B
  MAX_I2B	integer	$32767$	same as above for I2B integers
  MAX_I4B	integer	$2^{31}-1 \simeq 2.1\ 10^9$	same as above for I4B integers
  MAX_I8B	I8B	$2^{63}-1 \simeq 9.2\ 10^{18}$	same as above for I8B integers
  MAX_SP	SP	$\simeq 3.40\ 10^{38}$	same as above for SP floating-point
  MAX_DP	DP	$\simeq 1.80\ 10^{308}$	same as above for DP floating-point

  ¹ actual value may depend on hardware or compiler

• mathematical definitions,

  name	kind	value	definition
  QUARTPI	DP	$\pi/4$
  HALFPI	DP	$\pi/2$
  PI	DP	$\pi \simeq 3.14159\ldots$
  TWOPI	DP	$2\pi$
  FOURPI	DP	$4\pi$
  SQRT2	DP	$\sqrt{2}$
  EULER	DP	$\gamma \simeq 0.577\ldots$	Euler constant
  SQ4PI_INV	DP	$1/\sqrt{4\pi}$
  TWOTHIRD	DP	$2/3$
  DEG2RAD	DP	$\pi/180$	Degrees to Radians conversion factor
  RAD2DEG	DP	$180/\pi$	Radians to Degrees conversion factor

• and HEALPix specific definitions,

  name	type or kind	value	definition
  HPX_SBADVAL	SP	$-1.6375\ 10^{30}$	default sentinel value given to missing pixels in single precision data sets
  HPX_DBADVAL	DP	$-1.6375\ 10^{30}$	same as above for double precision data sets
  FILENAMELEN	integer	1024	default length in character of file names.
  HEALPIX_VERSION	character	“3.82”	current HEALPix package version.

EXAMPLE:

use healpix_types
real(kind=DP) :: dx
print*,' pi = ',PI

The value of PI, as well as all other healpix_types parameters are made known to the code