Refactor sum/product model (Trac #587)

[pkienzle]

We should be able to define mixture models using something as simple as:

from sasmodels.sasview_models import mixture
Model = mixture('sphere', 'cylinder')

rather than large template that is currently produced by a sum model. This will allow us to evolve the sasview model interface without breaking custom mixture models store in the .sasview/plugin_models. Similarly for product models.

See #715 for more info.

May also consider making mixture/product models as something generated by the user as needed as part of the fit page rather than having to name every mixture that they are using in their fits.

Ideally this would be done as part of the 4.0.0 release so we do not need to support the existing sasview plugin model definitions indefinitely.

Migrated from http://trac.sasview.org/ticket/587

{
    "status": "new",
    "changetime": "2018-07-04T18:50:52",
    "_ts": "2018-07-04 18:50:52.851215+00:00",
    "description": "We should be able to define mixture models using something as simple as:\n\n    from sasmodels.sasview_models import mixture\n    Model = mixture('sphere', 'cylinder')\n\nrather than large template that is currently produced by a sum model.  This will allow us to evolve the sasview model interface without breaking custom mixture models store in the .sasview/plugin_models. Similarly for product models.\n\nSee #583 for more info.\n\nMay also consider making mixture/product models as something generated by the user as needed as part of the fit page rather than having to name every mixture that they are using in their fits.\n\nIdeally this would be done as part of the 4.0.0 release so we do not need to support the existing sasview plugin model definitions indefinitely.\n",
    "reporter": "pkienzle",
    "cc": "",
    "resolution": "",
    "workpackage": "Beta Approximation Project",
    "time": "2016-06-22T18:27:40",
    "component": "SasView",
    "summary": "Refactor sum/product model",
    "priority": "major",
    "keywords": "",
    "milestone": "SasView Next Release +1",
    "owner": "",
    "type": "enhancement"
}

[pkienzle]

Trac update at 2016/08/16 15:55:41: pkienzle commented:

Generalize to:

Model = mixture('A + B', A='sphere', B='cylinder')

where the first value is an arbitrary expression and the keywords are the models to use in the expression.

[butlerpd]

Trac update at 2016/08/16 16:51:53:

• butler commented:

unfortunately ideal is not always practical. As discussed at meeting we don't have bandwidth to deal with for 4.0 release which is already way way late. Moving to +1

• butler changed milestone from "SasView 4.0.0" to "SasView Next Release +1"
• butler changed type from "defect" to "enhancement"
• butler changed workpackage from "SasView Bug Fixing" to "SasModels Redesign"

[butlerpd]

Trac update at 2018/07/04 18:50:52:

• butler commented:

As suggested by @richardh in ticket http://trac.sasview.org/ticket/1001 this is may be relevant to the beta approximation package so moving to that package.

HOWEVER ... we should check but I think this may already have been done? If so we should close this ticket as part of 4.2 release.

• butler changed workpackage from "SasModels Redesign" to "Beta Approximation Project"

[butlerpd]

The sum/mixture models were refactored long ago. Certainly by sasmodels 1.0.6 we now have so closing this as done