[Libreoffice-bugs] [Bug 137679] Implement a Kahan summation algorithm to reduce the numerical error in the total

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=137679

--- Comment #55 from b. <newbie-02 at gmx.de> ---
Created attachment 171782
  --> https://bugs.documentfoundation.org/attachment.cgi?id=171782&action=edit
testsheet kahan_sum with different versions

I don't see this working well yet.  

see attached sheet.  

Column A contains 100 times the three values 1E15; 0,1; -1E15.  

mathematically the sum over them should be 10.  

(difficult in FP-math, but solvable with Kahan summation).  

Column B contains partial sums, in cell B300 the sum over all values in
A1:A300.   

in cell C1 the value of B300 is copied, in C3:D6 the results calculated by
different calc versions and gnumeric.  

12.47500000000000 result calc 7.2.0.0.a0+ 2021-05-08  
12.50000000000000 result calc 7.1.4.0.0 2021-05-08  
12.50000000000000 result calc 6.1.6.3  
10.00000000000000 result gnumeric 1.12.17  

Status: correct results are possible, calc can't do it yet.  

I hope i haven't messed up my system? please check the results. if the pending
patches solve the problem just ignore this comment.

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