Rene Brun wrote:
> - Damir Buskulic has raised the question of precision in TAxis
> (float).
> Should we promote float to double in TAxis ? If yes, TH1
> constructors
> must be changed accordingly.
Hi Rene, Vincent and others,
For that question, I don't know if the this is the best way to go.
Clearly, you shouldn't need more than a float to describe an axis. Going
to double will probably solve the problem but not in an definite way,
though it's probably necessary. The problem is that all the coordinates
(so the axis) are relative to an origin that may be very far from the
viewing point, so one has to compute differences between big numbers,
which lead to the behaviour we've seen :
--------------
| |
|pad, axis...|
| |
| |
x----------------------------------------------------------
origin 6 6
0 10 10 +1
A solution should ensure that all the calculations made for drawing the
axis, histos, etc... never lead to such differences. It could be to have
a shift or reference point at the beginning of the pad. All calculations
would be made refering to this point and only at the end would one add,
for plotting numbers, the distance to the origin (add in double
precision obviously). This certainly leads to changes in TAxis but also
in TH1.
Just a thought...
Damir
--
=====================================================================
| Damir Buskulic | Universite de Savoie/LAPP |
| | Chemin de Bellevue, B.P. 110 |
| Tel : +33 (0)450091600 | F-74941 Annecy-le-Vieux Cedex |
| e-mail: buskulic@lapp.in2p3.fr | FRANCE |
=====================================================================
mailto:buskulic@lapp.in2p3.fr
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