Reported by User alessandra.delgiudice@…:

Dear SASview developer,

I found problems making fits with Sum|Multi plugin models in the 4.1.2 version. In brief:

In the 4.1.2 version I got a "Fitting did not converge!!!" error, whereas trying with the 4.1 version (installed on the same pc in a different folder) the fit worked.

I did a test with simulated data:

I created a Sum|Multi model with the dedicated tool: sphere_plus_hollowcylinder.py

I saved a calculated curve with parameters: p1_scale 0.5 p1_background 0 p1_sld 9.45 p1_sld_solvent 9.4 p1_radius 100 p2_scale 0.5 p2_background 0 p2_radius 50 p2_thickness 20 p2_length 1000 p2_sld 9.45 p2_sld_solvent 9.4 scale_factor 1

and 1400 points as sphere_and_hollow_cylinder_out.txt

I loaded this file as a data file to be fitted. I changed the sphere radius value from 100 to 50, and then clicked to "Fit". Nothing happened and I got a "Fitting did not converge!!!" error in the console.

I had an older installation file for SASview 4.1 and I installed it on my laptop in the folder SasView_4_1 instead of SasView (where the 4.1.2 version is)

The same test worked in this case.

When trying a similar test with a simpler model (sphere with default parameters), the fit starting from a different value of the sphere radius (100 instead of 50) worked with the 4.1.2 version.

I attach the sasview log as sasview_20180112.log. What I described starts with the line "2018-01-12 11:50:05,181 INFO —- SasView session started —-"

The paste functionality fails when you haven't used the "copy" button first. It should just do nothing and alert you in a nice way.

Each SasView seems to contain a function "random", on a par with "Iq".

However, I find no explanation of this function on the otherwise well written and informative page "Writing a Plugin Model" [1].

Could you please point me to an existing explanation of "random", or briefly improvise such explanation?

Thanks, Joachim

[1] ​http://www.sasview.org/docs/user/sasgui/perspectives/fitting/plugin.html