Tagging, Freezing, and Production Libraries

When analyzing data, it is important to keep a record of the analysis packages that was used to process the data. It is also important to have the ability to return to previous versions of analysis packages in order to reproduce results or to track down errors. Toward this purpose all of the CLAS analysis software is kept under the previously mentioned version management system called CVS. CVS allows the user to tag a set of software for later reference by essentially keeping track of what the code looked like at different points in the past. It is then possible to retrieve exact copies of the software which were used to process the data. For example, to retrieve a copy of the code used in production version 1-6, one would type

cvs checkout -r prod-1-6 packages

The production version number in the previous example refers to a set of software libraries and executables that were used to process the data and were tagged under CVS. Generally, a new production version is not necessary for every step in the cooking process. The times when production versions are needed will be discussed in section 5. Essentially, though, a production version is needed whenever a long term copy of the ``cooking'' results will be kept.

It is also necessary for a record of the calibration maps and the executables used to ``cook'' the data to be kept as well. Unfortunately, CVS does not economically keep binary files under management. Therefore, these files must be ``frozen'' by the person ``cooking'' the files. These files are ``frozen'' by having the write permissions removed from the file. These files are then used to process the data and a snapshot of them is stored to the tape silo.