<html xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;
mso-ligatures:none;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style>
</head>
<body lang="EN-US" link="blue" vlink="purple" style="word-wrap:break-word">
<div class="WordSection1">
<p class="MsoNormal">Hi all,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Any such changes should be coordinated with the recent suggestion of adding JPEGXL support to tile compression.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">If the IAU FITS WG is going through a period of rebuilding, the responsibility for maintaining FITS falls to Commission B2.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">We looked into support for 16-bit floats when working on FPACK and tile compression. As I recall, it may not be as standardized as 32-bit and 64-bit IEEE floats. There were also some video (?) standards that used real-number representations
that were fixed-point, not floating-point.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">128-bit formats may need to coexist with complex number representations. The motivations for both shorter than usual or longer than usual floating-point representations in FITS should flow from explicit science and engineering use cases.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Tiled 32-bit integer compression is actually quite elegant, and the noise-sensitive floating-point tile compression quite powerful, see Paper I and Paper II linked at
<a href="https://heasarc.gsfc.nasa.gov/fitsio/fpack/">https://heasarc.gsfc.nasa.gov/fitsio/fpack/</a>. There are also a number of interesting issues associated with efficient table compression, such as the benefit of transposing tables and shuffling the bytes.
Simply adding another data type won’t address all the issues.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I am unaware of any coherent benchmarks comparing the speed of using 16-bit floats versus FPACK-style floating point compression. This should also be a prerequisite. Are 16-bit floats widely used in other scientific disciplines?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Rob Seaman<o:p></o:p></p>
<p class="MsoNormal">Lunar and Planetary Laboratory<o:p></o:p></p>
<div style="mso-element:para-border-div;border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 1.0pt 0in">
<p class="MsoNormal" style="border:none;padding:0in"><o:p> </o:p></p>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<div id="mail-editor-reference-message-container">
<div>
<div>
<p class="MsoNormal" style="margin-left:.5in">On 7/23/25, 6:55 AM, "fitsbits" wrote:</p>
</div>
<p class="MsoNormal" style="margin-left:.5in"><br>
External Email<br>
<br>
On Wed 2025-07-23T13:34:54+0100 Thomas Robitaille via fitsbits hath writ:<br>
> I am aware of some modern projects that would benefit from having 16-bit<br>
> floats, since they consider it to be sufficient in precision to store very<br>
> large datasets, and using 16-bit floats would perform a lot better than<br>
> using compression on 32-bit floats for example, and 16-bit floats would<br>
> allow a larger dynamic range than using 16-bit ints with BSCALE/BZERO.<br>
<br>
This is not a breaking change, and with little more discussion than we<br>
already see today an informal agreement cold quickly go into use and<br>
then be adopted.<br>
I think the harder part about making this change is establishing<br>
the auspices under which the IAU FITS working group currently acts.<br>
<br>
--<br>
Steve Allen <sla@ucolick.org> WGS-84 (GPS)<br>
UCO/Lick Observatory--ISB 260 Natural Sciences II, Room 165 Lat +36.99855<br>
1156 High Street Voice: +1 831 459 3046 Lng -122.06015<br>
Santa Cruz, CA 95064 <a href="https://www.ucolick.org/~sla">
https://www.ucolick.org/~sla/</a> Hgt +250 m<br>
<br>
_______________________________________________<br>
fitsbits mailing list<br>
fitsbits@listmgr.nrao.edu<br>
<a href="https://listmgr.nrao.edu/mailman/listinfo/fitsbits">https://listmgr.nrao.edu/mailman/listinfo/fitsbits</a></p>
</div>
</div>
</div>
</body>
</html>