Tobyfit developments

From Tobyfit

Tobyfit Developments

15/1/2010

A new development version of Tobyfit GUI is available in the download area here, as SVN version 344. This version supports either Libisis or mgenie for graphics. However the zip file does not contain either of these packages and one or other must be download separately to allow the GUI to work. The version of mgenie supplied in the earlier distributions is not sufficient, as it lacks some updates needed for easy switching between libisis and mgenie. When using either Libisis or mgenie, it is necessary to get a recent version, which may not be generally available.

The zip file assumes that you have an existing Tobyfit installation, and unpacks to ./e-science/TobyfitLibIsis, e.g. if unpacked on Windows in c:\ it would become c:\e-science\TobyfitLibIsis.

The support tools, such as GaptkComputeTool box, MPICH2 and SRB commands (if using the grid option) should already be present from a previous install of Tobyfit. You can use an existing mgenie library by adding it to the PATH, e.g.:

addpath c:\e-science\mgenie

This needs to be done before running tobyfit.

The other enhancement of this version is the support of many more parameters in the cross section models. It is now possible to define an sqw broad or sharp model with up to 1000 parameters. This should be useful when dealing with many data sets that each require separate parameters. If using the Grid enabled version of Tobyfit, e.g. on NGS, it will be necessary to update the server binaries to enable support of more than 20 parameters. Models with 20 or fewer parameters will not require the server code to updated.

To use more than 20 parameters in a model it is necessary to first set up a new sqw_broad.f or sqw_sharp.f which defines a new model with more than 20 parameters. The special comments section must define the new parameters. For example if, just for testing, we want to change model 601 to use p70 instead of p7 to represent the gamma term, then the comment section would become:

!-------------------------------------
!TF_MODEL 601 cobalt spin waves with uni DSHO damping
!TF_MODEL_PARAM  4  1 2 3 70
!TF_MODEL_PNAMES Amplitude 12JS(AA) 12JS(AB) gamma

A scrollable table of 70 parameters will be created in the cross section tab when the GUI is started with this new sqw_broad.f file. At present the parameter table will sized to the largest number of parameters used by any model defined in the sqw subroutines.

18/3/10

Changes have been made to the random numbers used in the Monte Carlo integration methods. A bug has been fixed in the random number (non-Sobel) method (MC_TYPE=0, not the default method). This bug was not present in the original Tobyfit software. MC_Type=0 simulations now use a unique seed for each call to allow testing of the results with respect to the number of steps used.

Two new experimental values of MC_Type are supported. MC_Type=2 is random number based Monte Carlo but with the seed not reset between Chi^2 evaluations (the seed is reset for differential calculations). MC_Type=3 is similar to MC_Type=1 except using a (non-reset) Sobel sequence.

For users within Isis, an extra computational resource has been added, the mountainview cluster. This grid resource is not generally available and requires extra steps to set up access.