[x3d-public] X3DJSAIL -- precision stripping of trailing zeroes and decimal point

[Don Brutzman]

[cc: x3d public list]

John, thanks for requesting that trailing zeros get stripped.  Now implemented using new utility function

	http://www.web3d.org/specifications/java/javadoc/org/web3d/x3d/java/fields/X3DConcreteField.htmlstripTrailingZeroes-double-
	http://www.web3d.org/specifications/java/javadoc/org/web3d/x3d/java/fields/X3DConcreteField.htmlstripTrailingZeroes-float-

Surprisingly this took a little doing, apparently it is an edge case in Java.

For anyone interested, useful (though high variance) references are

	StackOverflow: Remove trailing zeros from double (String manipulation solution)
	http://stackoverflow.com/questions/11284938/remove-trailing-zeros-from-double

	StackOverflow: How to nicely format floating numbers to String without unnecessary decimal 0? ("In short" solution)
	http://stackoverflow.com/questions/11284938/remove-trailing-zeros-from-double

Looking for simplicity and high performance among various approaches, I adapted a regular expression (regex) version from one alternative within the first forum entry as

	public static String stripTrailingZeroes (float value)
	{
		// regex to strip trailing zeroes, then strip trailing decimal point
		return String.valueOf(value).replaceAll("[0]*$", "").replaceAll("\\.$", "");
	}

regex decipherment:

- [0]* zero or more 0 characters
- $    end of line anchor
- \\   escaped, literal backslash character \
- \\.  escaped, literal decimal point

None of the code is profiled yet but no discernible slowdown seen - as expected, regex processing appears to be extremely efficient.

Future work #1: we may need to coerce English locale inside X3DJSAIL in order to force the output of decimal points as period . instead of comma , (as is common in Europe).

Future work #2: this pattern is good to add to our X3D Regex page when that starts moving again.

	http://www.web3d.org/specifications/X3dRegularExpressions.html

Future work #3: we should likely consider adding such stripping of trailing zeroes from numeric types as part of X3D Canonical Form since such characters are superfluous and do not change the graphical contents of a file.

	ISO/IEC 19776-3:200x X3D Compressed binary encoding -- 4 Concepts
	4.2.3 X3D canonical form
	http://www.web3d.org/documents/specifications/19776-3/V3.1/Part03/concepts.html#X3DCanonicalForm

Interestingly, stripping the trailing .0 characters seems to improve readability too.  Canonicalization (C14N) suggestion posted for eventual resolution using Mantis issue tracker.

Test reports welcome.

	http://www.web3d.org/specifications/java/X3dJavaSceneAuthoringInterface.html

Have fun with X3DJSAIL Java!   8)
     

On 2/3/2017 5:11 PM, Don Brutzman wrote:
> you are right (of course) and i will look for the correct formatting invocation in Java to accomplish that approach.
>
> On 2/2/2017 5:28 AM, yottzumm at gmail.com wrote:
>>>> Re: removing precision of .0 floats and doubles…often this precision is added by the software, so we would be restoring it.
>>
>> Don Brutzman wrote:
>>
>>> hmmm let's look closely at those please.  i think that precision is defined by data type so either 0 or 0. or 0.0 are equivalent.
>>
>>> stripping trailing zeroes reduces file size without loss of information.  We probably should add that to C14N binary encoding rules
>>
>> I suggest that the X3DJSAIL toString() field methods for floats and doubles (and their arrays, vectors, matrices, MF fields, etc) strip off trailing .0’s – Removing the .0 should save space if not anything else.  This will help with roundtrip comparisons.  I believe this is in many places, but I could be wrong.  Perhaps create a helper method which does the precision stripping.  In a more scientific sense, the precision is being added by Java I think…just need to use the right method for printing in out (in Number, perhaps?).  This is basically happening often when a float is encountered which is an integer.  If you want specifics, I will try to create diffs.

all the best, Don
-- 
Don Brutzman  Naval Postgraduate School, Code USW/Br       brutzman at nps.edu
Watkins 270,  MOVES Institute, Monterey CA 93943-5000 USA   +1.831.656.2149
X3D graphics, virtual worlds, navy robotics http://faculty.nps.edu/brutzman