Change request #1547
ctbkgcube should set parameter boundaries of output model
| Status: | Closed | Start date: | 10/07/2015 | |
|---|---|---|---|---|
| Priority: | Normal | Due date: | ||
| Assigned To: |  Knödlseder Jürgen | % Done: | 100% | |
| Category: | - | |||
| Target version: | 1.0.0 | |||
| Duration: |
Description
I realised that in some analyses, we have convergence problems when the parameters are not properly constrained.
Running ctbkgcube, the output background model parameter Prefactor is limited to [0.0; infty[.
The problem occurs e.g. in csspec in binned mode (all curvatures are zero for some energy bins). Limiting the Prefactor to [0.01;100] solved the problem.
I therefore propose to change the following lines in ctbkgcube:
GModelSpectralPlaw spectral(1.0, 0.0, GEnergy(1.0, "TeV"));
GCTAModelCubeBackground model(spectral);
to
GModelSpectralPlaw spectral(1.0, 0.0, GEnergy(1.0, "TeV"));
spectral["Prefactor"].min(0.01);
spectral["Prefactor"].max(100.0);
GCTAModelCubeBackground model(spectral);
Recurrence
No recurrence.
History
#1
Updated by Knödlseder Jürgen over 8 years ago
Agree to constrain the parameters. Note that there is range method that allows to set both boundaries at once, i.e.
spectral["Prefactor"].range(0.01, 100.0);We might also constrain the index to some plausible values, for example [-1.0, 1.0], but we should probably check first that this does not create any problem.
#2
Updated by Mayer Michael over 8 years ago
Even better to use the range method. The index is currently constrained to [-10,10] which of course is a large range. I agree that further constraining might be good and I guess [-1,1] should be fine here. To be careful we could however think about [-5,5]?
#3
Updated by Knödlseder Jürgen over 8 years ago
Also fine. I was not aware that the index was already constrained. Whatever fit your needs should be fine, we can always revise this later when we have more experience with it.
#4
Updated by Mayer Michael over 8 years ago
I guess in order not to break someones analysis, we could use [-5.0,5.0]. This range should still be appropriate to fit indices around 0.0.
I was not aware that the index was already constrained.
This happens on construction in GModelSpectralPlaw::init_members().
#5
Updated by Knödlseder Jürgen over 8 years ago
Mayer Michael wrote:
I guess in order not to break someones analysis, we could use [-5.0,5.0]. This range should still be appropriate to fit indices around 0.0.
I was not aware that the index was already constrained.
This happens on construction in
GModelSpectralPlaw::init_members().
should remember better what I have coded ...
#6
Updated by Mayer Michael over 8 years ago
Should I create a branch, or do you implement this right away?
#7
Updated by Knödlseder Jürgen over 8 years ago
- Status changed from New to Closed
- Assigned To set to Knödlseder Jürgen
- Target version set to 1.0.0
- % Done changed from 0 to 100
Just implemented the change (is in devel).