bugGNU Octave - Bugs: bug #43311, symbolic: Wrong expected value in...


bug #43311: symbolic: Wrong expected value in symfsolve test

Submitted by:  Rafael Laboissiere <rlaboiss>
Submitted on:  Sun 28 Sep 2014 12:07:32 AM UTC  
Category:  Octave Forge Package Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Incorrect Result
Status:  Wont Fix Assigned to:  None
Originator Name:  Open/Closed:  Closed
Release:  dev Operating System:  GNU/Linux

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Sun 22 Feb 2015 06:29:37 AM UTC, comment #1: 

The new symbolic package does not have a symfsolve function, instead providing what looks like a Matlab compatible solve function operating on symbolic types. Closing this bug as won't fix since the symfsolve function is gone along with the old symbolic package.

Mike Miller <mtmiller>
Project Administrator
Sun 28 Sep 2014 12:07:32 AM UTC, original submission:  

For some reason that I do not really understand, the last test in file symfsolve.m is giving now (with Octave 3.8.2) a different result from what it used to give before, even though the solution that is found is fully valid.  This is perhaps due to recent changes in the fsolve function, which is in Octave core.  Here is what I obtain now:

octave:1> symbols
octave:2> x = sym ("x");
octave:3> y = sym ("y");
octave:4> f = x ^ 2 + 3 * x - 1;
octave:5> g = x * y - y ^ 2 + 3;
octave:6> assert (symfsolve ({f, g}, {y==1,x==2}), [1.89004; 0.30278]', 1e-5);
error: ASSERT errors for:  assert (symfsolve ({f, g}, {y == 1, x == 2}),[1.89004; 0.30278]',1e-5)

  Location  |  Observed  |  Expected  |  Reason
    (1)        -1.5873        1.89       Abs err 3.4773 exceeds tol 1e-05

The obvious fix is to change the test in inst/symfsolve.m to read:

%!assert (symfsolve ({f, g}, {y==1,x==2}), [-1.58727; 0.30278]', 1e-5);

Rafael Laboissiere <rlaboiss>


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    Follow 2 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2015-02-22 mtmiller StatusNone => Wont Fix
        Open/ClosedOpen => Closed

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