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,

0

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 10³⁰ with the least margin (hereafter single precision)

DP integer 8 same as above for the range 10^-200 to 10²⁰⁰ (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,

0

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 I4B 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	$\pi$
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.

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

Eric Hivon 2010-06-18

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