star-line

Structure for accelerating line importance sampling
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sln-build.1 (5881B)


      1 .\" Copyright (C) 2022, 2026 |Méso|Star> (contact@meso-star.com)
      2 .\" Copyright (C) 2026 Université de Lorraine
      3 .\" Copyright (C) 2022 Centre National de la Recherche Scientifique
      4 .\" Copyright (C) 2022 Université Paul Sabatier
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     18 .Dd January 29, 2026
     19 .Dt SLN-BUILD 1
     20 .Os
     21 .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
     22 .Sh NAME
     23 .Nm sln-build
     24 .Nd build an acceleration structure for line importance sampling
     25 .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
     26 .Sh SYNOPSIS
     27 .Nm
     28 .Op Fl hsv
     29 .Op Fl e Ar polyline_opt Ns Op : Ns Ar polyline_opt No ...
     30 .Op Fl l Ar line_profile
     31 .Op Fl o Ar accel_struct
     32 .Fl P Ar pressure
     33 .Fl T Ar temperature
     34 .Fl m Ar molparams
     35 .Fl x Ar mixture
     36 .Op Ar lines
     37 .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
     38 .Sh DESCRIPTION
     39 .Nm
     40 constructs a data structure designed to accelerate the sampling by
     41 importance of the spectral lines defined for a gas mixture under given
     42 thermodynamic conditions, from a spectroscopic parameters database.
     43 The generated structure is a binary tree that stores a polyline of
     44 spectral data at each node that it encompasses.
     45 .Pp
     46 The input spectroscopic data, i.e., the line list and isotopological
     47 metadata, are formatted in HITRAN file formats.
     48 If not provided, the list of lines is read from standard input.
     49 .Pp
     50 The options are as follows:
     51 .\""""""""""""""""""""""""""""""""""
     52 .Bl -tag -width Ds
     53 .It Fl e Ar polyline_opt Ns Op : Ns Ar polyline_opt No ...
     54 Configure the polylines, i.e., the data used to encode the shape of the
     55 spectrum in the acceleration structure.
     56 .Pp
     57 The polyline options are as follows:
     58 .Bl -tag -width Ds
     59 .It Cm err= Ns Ar decimation_error
     60 Relative error used to simplifly polylines.
     61 The larger it is, the coarser the polylines obtained, and therefore the
     62 less memory it uses.
     63 The default value is 0.01.
     64 .It Cm mesh= Ns Ar mesh_type
     65 Define how the polylines are meshed.
     66 .Pp
     67 The supported
     68 .Ar mesh_type
     69 values are as follows:
     70 .Bl -tag -width Ds
     71 .It Cm fit
     72 The polylines fit the spectrum data.
     73 .It Cm upper
     74 The polylines define an upper limit for the spectrum they encode.
     75 This is the default behavior.
     76 .El
     77 .It Cm vcount= Ns Ar vertex_count_hint
     78 Recommendation for the number of vertices around the center of the line.
     79 The fewer vertices there are, the coarser the polyline of a line and the
     80 smaller the memory usage.
     81 The default value is 16.
     82 .El
     83 .It Fl h
     84 Display short help and exit.
     85 .\""""""""""""""""""""""""""""""""""
     86 .It Fl l Ar line_profile
     87 Defines the line profile.
     88 Currently,
     89 .Cm voigt
     90 is the only supported profile and therefore the default value.
     91 .\""""""""""""""""""""""""""""""""""
     92 .It Fl o Ar accel_struct
     93 Output file.
     94 If not defined, the acceleration structure is written to standard output.
     95 .\""""""""""""""""""""""""""""""""""
     96 .It Fl P Ar pressure
     97 Pressure of the gaz mixture, in atmospheres
     98 .Pq 1 atm = 1.01315 bar .
     99 .\""""""""""""""""""""""""""""""""""
    100 .It Fl s
    101 Specifies that input lines are formatted according to the binary format
    102 as written by the
    103 .Xr shtr 1
    104 utility, and not according to the HITRAN format.
    105 This format is more compact, allowing for faster loading of line data.
    106 .\""""""""""""""""""""""""""""""""""
    107 .It Fl T Ar temperature
    108 Temperature of the gaz mixture, in Kelvin.
    109 .\""""""""""""""""""""""""""""""""""
    110 .It Fl m Ar molparams
    111 Isotopologue metadata in HITRAN format.
    112 .\""""""""""""""""""""""""""""""""""
    113 .It Fl v
    114 Make
    115 .Nm
    116 verbose.
    117 Multiple
    118 .Fl v
    119 options increase the verbosity.
    120 The maximum is 3.
    121 .\""""""""""""""""""""""""""""""""""
    122 .It Fl x Ar mixture
    123 Composition of the gaz mixture in
    124 .Xr sln-mixture 5
    125 format.
    126 If a molecule is absent from this file, its concentration in the mixture
    127 is assumed to be zero.
    128 .El
    129 .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
    130 .Sh EXIT STATUS
    131 .Ex -std
    132 .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
    133 .Sh EXAMPLES
    134 Build a structure that accelerates importance sampling of the lines in
    135 the H2O spectrum, between 0 and 50 cm^-1, at a pressure of 1 atm and a
    136 temperature of 292 K.
    137 Use the default options to mesh the spectrum, so that the resulting
    138 structure represents an upper bound on the spectral data:
    139 .Bd -literal -offset Ds
    140 sln-build -P 1 -T 292 -o H2O_0-50_HITAMP2010_tree.bin \e
    141   -m /path/to/hitran/molparams.txt -x mixture.txt \e
    142   /path/to/hitran//H2O/01_0-50_HITEMP2010.par
    143 .Ed
    144 .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
    145 .Sh SEE ALSO
    146 .Xr shtr 1 ,
    147 .Xr sln-mixture 5
    148 .Rs
    149 .%A Yaniss Nyffenegger-Péré et al.
    150 .%T Spectrally refined unbiased monte carlo estimate of the earth's \
    151 global radiative cooling
    152 .%J Proceedings of the National Academy of Sciences
    153 .%P e2315492121
    154 .%V 121
    155 .%N 5
    156 .%D 2024
    157 .Re
    158 .Rs
    159 .%T The HITRAN Database
    160 .%U https://hitran.org/
    161 .Re
    162 .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
    163 .Sh STANDARDS
    164 .Rs
    165 .%A L.S. Rothman et al.
    166 .%T The HITRAN2012 molecular spectroscopic database
    167 .%J Journal of Quantitative Spectroscopy & Radiative Transfer
    168 .%V 130
    169 .%P pp. 4\(en50
    170 .%D 2013
    171 .Re
    172 .Pp
    173 .Rs
    174 .%A L.S. Rothman et al.
    175 .%T HITEMP, the high-temperature molecular spectroscopic database
    176 .%J Journal of Quantitative Spectroscopu & Radiative Transfer
    177 .%V 111
    178 .%P pp. 2139\(en2150
    179 .%D 2010
    180 .Re