Number of Jacobian File Dumps#

Number of Jacobian File Dumps = <integer>

Description / Usage#

This routine will dump a serial machine independent binary file out to disk containing the Jacobian. The file is meant to be used by the auxiliary program, checkGomaJac, to compare two versions of the Jacobian. Ancillary data meant to enhance the printouts in checkGomaJac are also output to the file. The card takes one mandatory integer variable.

<integer>: If the integer is a positive number, n, then Goma will dump the first n Jacobians created (for any reason) to the current directory. If the integer is a negative value, -n, then Goma will dump a single Jacobian, the n’th Jacobian created, to the current directory.

The dumped files are named matrix.000, matrix.001, etc. Overwrites of files are allowed to occur. The files themselves are written out using the XDR protocol layer (easy, quick, and machine portable). The VBR format is used to write files out, even if the internal format used by Goma is MSR. Thus, VBR and MSR formatted Jacobians may be compared. Frontal Solver Jacobians are not compatible. The algorithm used is also compatible with parallel jobs using Goma. In other words, the Jacobian file dumped out for an 8 processor Goma run should be identical to the file dumped out by a single processor run.

In order to use this feature, it is necessary to compile Goma with the MATRIX_DUMP flag defined.

To compare two Jacobian files previously dumped out for compatibility, run checkGomaJac offline:

checkGomaJac   matrix1   matrix2

checkGomaJac will compare each entry in the row and column scaled matrices and print out in an annotated format the entries containing the largest differences.

Examples#

Number of Jacobian File Dumps = 2

Technical Discussion#

This capability has proven itself to be very useful in tracking changes to the Jacobian due to differences in the machine architecture, number of processes, and due to changes in the source code over time. The comparison is done using the standard RTOL, ATOL logic found in ODE solvers. In other words, a weighting vector of the form,

EQUATION

is created for each Jacobian entry, J_i. Then, a determination of the difference between J_{i`and J:sub:`i} by the following formula:

EQUATION

w_i is also used in the Jacobian column scalings, before the standard row sum scaling is applied.

Internal Sandia users can find the auxiliary program, checkGomaJac, in the directory / home/goma/arch/linux/bin on the Linux compute server, and in other ‘arch’ subdirectories for other platforms. External users should contact Goma support staff to obtain the tool.