Re: [xsl] Q on XSLT number calculation precision

[Michel Hendriksen <michel.hendriksen@xxxxxxxxx>]

It might also depend on the order in which calculations are done. Some
processors could maybe optimize a bit and change the outcome by doing
so.

On Fri, Feb 18, 2011 at 1:04 AM, Michael Kay <mike@xxxxxxxxxxxx> wrote:
> On 17/02/2011 22:56, Hermann Stamm-Wilbrandt wrote:
>>
>> Hello,
>>
>> are there any requirements on precision of number calculations for XSLT?
>
> Your question actually seems to be about XSLT 1.0.
>
> XSLT 1.0 requires use of IEEE double precision floating point. But I
suspect
> there's sufficient wriggle-room that two processors can produce different
> results and still claim conformance.
>
> Michael Kay
> Saxonica
>
>> I wrote stylesheet [3] just summing the first 1000 (small) terms of this
>> nice identity on binomial coefficient reciprocals I proved 28 years ago:
>>
>> $$ \sum_{i=j+1}^{\infty}{}^1/_{i\choose j}={}^1/_{(j-1)} , ~ j\ge 2 $$
>>
>> Pascal.xml [2] just starts the computation with jmax=12 and terms=1000.
>>
>> I opened Pascal.xml in the big five browsers, arranged them in order to
>> easily compare their results and took screenshot [3] from that.
>>
>> Not surprisingly the most left and most right column (Chrome and Safari)
>> are identical (same XSLT engine).
>>
>> Interestingly Firefox and Internet Explorer produce nearly identical
>> values.
>>
>> For j<=7 Opera is fine, but for j>=8 something goes really wrong.
>> The sum of the 1000 terms becomes bigger than then infinity sum :-)
>>
>>
>> [1]
>>
>>
http://stamm-wilbrandt.de/en/xsl-list/Chrome_FF_IE_Opera_Safari-XSLT_precisio
n.gif
>> [2] http://stamm-wilbrandt.de/en/blog/Pascal.xml
>> [3] http://stamm-wilbrandt.de/en/blog/Pascal.xsl
>>
>>
>> Mit besten Gruessen / Best wishes,
>>
>> Hermann Stamm-Wilbrandt
>> Developer, XML Compiler, L3
>> Fixpack team lead
>> WebSphere DataPower SOA Appliances
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