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Re: [Axiom-developer] severe (!) bug in normalize
From: |
Martin Rubey |
Subject: |
Re: [Axiom-developer] severe (!) bug in normalize |
Date: |
05 Dec 2006 22:59:30 +0100 |
User-agent: |
Gnus/5.09 (Gnus v5.9.0) Emacs/21.4 |
Dear Francois,
Francois Maltey <address@hidden> writes:
> I'm testing some patchs in expr.spad.
> On my today-version I get :
>
> (64) -> T := t^(n^2)*sqrt(1+t)^n
> 2
> n +-----+n
> (64) t \|t + 1
> Type: Expression Integer
> (65) -> T/subst (T, n=n-1)
> 2n - 1 +-----+
> (65) t \|t + 1
> Type: Expression Integer
> (68) -> normalize (T/eval (T, n=n-1))
> +-----+ (2n - 1)log(t)
> (68) \|t + 1 %e
> Type: Expression Integer
Although this is very nice (I tried it!), it only steps around the bug in
rischNormalize, since the latter is not called with the same arguments: your
patches make axiom simplify T/eval(T, n=n-1) right away. Although this is a
very good thing, I suspect that the bug in rischNormalize will surface under
other circumstances, too.
I will comment on your patches in a separate email tomorrow, but I'd like to
express my joy about your work on EXPR and friends. I do have some - hopefully
constructive - critisism, though.
Meanwhile I did a bit of tracing. It seems likely that the bug occurs in
expeval, possibly in goodCoef. Here is the relevant bit of the trace:
1<enter ElementaryFunctionStructurePackage.expeval,119 :
+-----+
n log(t) n log(\|t + 1 )
%e %e
arg1= ---------------------------
+-----+
(n - 1)log(\|t + 1 )
%e
+-----+
+-----+ n log(t) +-----+ (n - 1)log(\|t + 1 )
arg2= [log(t),\|t + 1 ,%e ,log(\|t + 1 ),%e ]
+-----+
n log(\|t + 1 )
arg3= %e
arg4= [0,0,1,1]
1<enter ElementaryFunctionStructurePackage.goodCoef,142 :
arg1= [0,0,1,1]
+-----+
+-----+ n log(t) +-----+ (n - 1)log(\|t + 1 )
arg2= [log(t),\|t + 1 ,%e ,log(\|t + 1 ),%e ]
arg3= exp
1>exit ElementaryFunctionStructurePackage.goodCoef,142 :
n log(t)
[index= 3,ker= %e ]
1>exit ElementaryFunctionStructurePackage.expeval,119 :
+-----+ 2
n log(\|t + 1 )
(%e ) n log(t)
[func= -------------------------, kers= [%e ],
+-----+ 2
(n - 1)log(\|t + 1 )
(%e )
+-----+
n log(\|t + 1 )
%e
vals= [----------------------]]
+-----+
(n - 1)log(\|t + 1 )
%e
Note that the expeval replaces the elements of "kers" with the elements of
"vals", but here, these are clearly not equivalent: kers contains t^n, vals
however sqrt(t+1).
Maybe this is simply an index mismatch: The length of the fourth argument to
expeval and goodCoef is four, but I have the feeling that it is meant to refer
to the elements of the second argument which are of the form exp... or log...,
and thus sqrt(t+1) should not be counted. In other words, maybe goodCoef should
rather return [index= 4, ker= log(sqrt(t+1))] or so.
Any ideas?
This really calls for unit testing!!!
Martin
- [Axiom-developer] severe (!) bug in normalize, Martin Rubey, 2006/12/05
- Re: [Axiom-developer] severe (!) bug in normalize, Francois Maltey, 2006/12/05
- [Axiom-developer] Re: severe (!) bug in normalize, Waldek Hebisch, 2006/12/05
- [Axiom-developer] Re: severe (!) bug in normalize, Martin Rubey, 2006/12/06
- [Axiom-developer] Re: severe (!) bug in normalize, Martin Rubey, 2006/12/06
- [Axiom-developer] Re: severe (!) bug in normalize, Waldek Hebisch, 2006/12/06
- [Axiom-developer] Re: severe (!) bug in normalize, Martin Rubey, 2006/12/06
- [Axiom-developer] Re: severe (!) bug in normalize, Waldek Hebisch, 2006/12/06
- [Axiom-developer] Re: severe (!) bug in normalize, Waldek Hebisch, 2006/12/06
- [Axiom-developer] Re: severe (!) bug in normalize, Martin Rubey, 2006/12/06
- Re: [Axiom-developer] Re: severe (!) bug in normalize, Francois Maltey, 2006/12/06
- [Axiom-developer] Re: severe (!) bug in normalize, Waldek Hebisch, 2006/12/06