#11934: Symbolic simplification error
-------------------------+--------------------------------------------------
Reporter: mjo | Owner: burcin
Type: defect | Status: new
Priority: major | Milestone: sage-4.7.3
Component: symbolics | Keywords:
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
-------------------------+--------------------------------------------------
Old description:
> I ran into this today with a real function. Sorry I don't have a shorter
> test case. The attached file should show a simplification which, as far
> as I can tell, is invalid.
New description:
I ran into this today with a real function. Sorry I don't have a shorter
test case. The attached file should show a simplification which, as far as
I can tell, is invalid.
{{{
sage: f = QQ(0.25)*(sqrt(2) - 2)*(x + 1)*x**3 - QQ(3)/QQ(8)*(sqrt(2) -
2)*(x + 1)*x**2 - QQ(0.25)*(sqrt(2) - 2)*(2*(3*sqrt(2) - 2)*x**2 -
2*(sqrt(2) - 1)*x + sqrt(-8*(4*sqrt(2) - 7)*x**4 + 16*(3*sqrt(2) - 5)*x**3
- 8*(2*sqrt(2) - 3)*x - 4*x**2 + 4) - 4*sqrt(2) + 2)*x**3/(sqrt(2)*x**2 +
sqrt(2)*x - 2*sqrt(2)) - 1/24*(x + 1)**3*(x**3 - 3*x + 2) +
QQ(3)/QQ(8)*(sqrt(2) - 2)*(2*(3*sqrt(2) - 2)*x**2 - 2*(sqrt(2) - 1)*x +
sqrt(-8*(4*sqrt(2) - 7)*x**4 + 16*(3*sqrt(2) - 5)*x**3 - 8*(2*sqrt(2) -
3)*x - 4*x**2 + 4) - 4*sqrt(2) + 2)*x**2/(sqrt(2)*x**2 + sqrt(2)*x -
2*sqrt(2)) - QQ(1)/QQ(16)*(x + 1)**2*(2*(sqrt(2) - 3)*x**3 - (3*sqrt(2) -
8)*x**2 + 2*x + sqrt(2) - 4) + QQ(1)/QQ(8)*(x + 1)*sqrt(2) +
QQ(1)/QQ(96)*(x**3 - 3*x + 2)*(2*(3*sqrt(2) - 2)*x**2 - 2*(sqrt(2) - 1)*x
+ sqrt(-8*(4*sqrt(2) - 7)*x**4 + 16*(3*sqrt(2) - 5)*x**3 - 8*(2*sqrt(2) -
3)*x - 4*x**2 + 4) - 4*sqrt(2) + 2)**3/(sqrt(2)*x**2 + sqrt(2)*x -
2*sqrt(2))**3 + 1/32*(2*(3*sqrt(2) - 2)*x**2 - 2*(sqrt(2) - 1)*x +
sqrt(-8*(4*sqrt(2) - 7)*x**4 + 16*(3*sqrt(2) - 5)*x**3 - 8*(2*sqrt(2) -
3)*x - 4*x**2 + 4) - 4*sqrt(2) + 2)**2*(2*(sqrt(2) - 3)*x**3 - (3*sqrt(2)
- 8)*x**2 + 2*x + sqrt(2) - 4)/(sqrt(2)*x**2 + sqrt(2)*x - 2*sqrt(2))**2 -
QQ(0.25)*x - QQ(1)/QQ(8)*(2*(3*sqrt(2) - 2)*x**2 - 2*(sqrt(2) - 1)*x +
sqrt(-8*(4*sqrt(2) - 7)*x**4 + 16*(3*sqrt(2) - 5)*x**3 - 8*(2*sqrt(2) -
3)*x - 4*x**2 + 4) - 4*sqrt(2) + 2)*sqrt(2)/(sqrt(2)*x**2 + sqrt(2)*x -
2*sqrt(2)) + QQ(0.25)*(2*(3*sqrt(2) - 2)*x**2 - 2*(sqrt(2) - 1)*x +
sqrt(-8*(4*sqrt(2) - 7)*x**4 + 16*(3*sqrt(2) - 5)*x**3 - 8*(2*sqrt(2) -
3)*x - 4*x**2 + 4) - 4*sqrt(2) + 2)/(sqrt(2)*x**2 + sqrt(2)*x - 2*sqrt(2))
- QQ(0.25)
sage: f.full_simplify()
-1/24*(sqrt(2)*x^8 - 2*(sqrt(2) - 3)*x^7 - (14*sqrt(2) - 15)*x^6 +
10*(9*sqrt(2) - 13)*x^5 - (93*sqrt(2) - 128)*x^4 - 4*(9*sqrt(2) - 14)*x^3
+ (58*sqrt(2) - 77)*x^2 + 4*(sqrt(2) - 2)*x - sqrt(2*(4*sqrt(2) - 7)*x^2 +
4*(sqrt(2) - 2)*x - 1)*((16*I*sqrt(2) - 28*I)*x^4 + (-24*I*sqrt(2) +
40*I)*x^3 + (8*I*sqrt(2) - 12*I)*x + 2*I*x^2 - 2*I) - 8*sqrt(2) +
10)/(sqrt(2)*x^2 + 4*sqrt(2)*x + 4*sqrt(2))
}}}
--
Comment(by kcrisman):
Can you be more specific about the invalidity? I think the plot errors
are because of the imaginary pieces. Remember, these simplifications are
not supposed to be 100 percent valid at all times; especially with roots
there are branch issues, unfortunately. The `f` in question is pretty
long - any sense as to where it might simplify in an unusual way?
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11934#comment:1>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/sage-trac?hl=en.
