| 1 | Sasmodels |
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| 2 | ========= |
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| 3 | |
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| 4 | Theory models for small angle scattering. |
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| 5 | |
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| 6 | The models provided are usable directly in the bumps fitting package and |
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| 7 | in the sasview analysis package. If OpenCL is available, the models will |
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| 8 | run much faster. If not, then precompiled versions will be included with |
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| 9 | the distributed package. New models can be added if OpenCL or a C compiler |
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| 10 | is available. |
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| 11 | |
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| 12 | Example |
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| 13 | ------- |
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| 14 | |
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| 15 | The example directory contains a radial+tangential data set for an oriented |
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| 16 | rod-like shape. |
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| 17 | |
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| 18 | The data is loaded by sas.dataloader from the sasview package, so sasview |
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| 19 | is needed to run the example. |
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| 20 | |
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| 21 | To run the example, you need sasview, sasmodels and bumps. Assuming these |
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| 22 | repositories are installed side by side, change to the sasmodels/example |
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| 23 | directory and enter:: |
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| 24 | |
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| 25 | PYTHONPATH=..:../../sasview/src ../../bumps/run.py fit.py \ |
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| 26 | cylinder --preview |
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| 27 | |
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| 28 | See bumps documentation for instructions on running the fit. With the |
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| 29 | python packages installed, e.g., into a virtual environment, then the |
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| 30 | python path need not be set, and the command would be:: |
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| 31 | |
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| 32 | bumps fit.py cylinder --preview |
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| 33 | |
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| 34 | The fit.py model accepts up to two arguments. The first argument is the |
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| 35 | model type, which has been defined for cylinder, capped_cylinder, |
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| 36 | core_shell_cylinder, ellipsoid, triaxial_ellipsoid and lamellar. The |
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| 37 | second argument is view, which can be radial or tangential. To fit |
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| 38 | both radial and tangential simultaneously, use the word "both". |
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| 39 | |
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| 40 | Notes |
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| 41 | ----- |
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| 42 | |
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| 43 | cylinder.c + cylinder.py is the cylinder model with renamed variables and |
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| 44 | sld scaled by 1e6 so the numbers are nicer. The model name is "cylinder" |
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| 45 | |
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| 46 | cylinder_clone.c + cylinder_clone.py is the cylinder model using the |
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| 47 | same interface as the sasview, including calling the model CylinderModel, |
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| 48 | so that it can be used as a drop-in replacement for the sasview cylinder |
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| 49 | model. |
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| 50 | |
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| 51 | lamellar.py is an example of a single file model with embedded C code. |
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| 52 | |
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| 53 | Note: may want to rename form_volume to calc_volume and Iq/Iqxy to |
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| 54 | calc_Iq/calc_Iqxy in model interface. Similarly ER/VR go to calc_ER/calc_VR. |
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| 55 | |
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| 56 | Note: It is possible to translate python code automatically to opencl, using |
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| 57 | something like numba, clyther, shedskin or pypy, so maybe the kernel functions |
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| 58 | could be implemented without any C syntax. |
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| 59 | |
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| 60 | Note: angular dispersion in theta is probably not calculated correctly, but |
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| 61 | is left this way for compatibility with sasview. |
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| 62 | |
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| 63 | Magnetism hasn't been implemented yet. We may want a separate Imagnetic |
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| 64 | calculator with the extra parameters and calculations. We should |
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| 65 | return all desired spin states together so we can share the work of |
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| 66 | computing the form factors for the different magnetic contrasts. This |
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| 67 | will mean extending the data handler to support multiple cross sections |
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| 68 | in the same data set. |
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| 69 | |
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| 70 | Need to implement an example kernel directly in python. Polydispersity |
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| 71 | loops should be generated automatically as they are for the OpenCL models. |
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| 72 | The kernels should be vectorized across Q. These will need vectorized |
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| 73 | versions of numerical quadrature if we want to get reasonable performance. |
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| 74 | |
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