4.1.5. Inversion Program

Both the forward and inverse problems are solved using the tdoctree_v2.exe executable program. In each case, format of the input file (denoted here as tdoctree.inp) is the same. In the case of forward modeling however, some lines in the input file are omitted.

4.1.5.1. Running the Program

Unlike some other UBC-GIF programs, the mpiexec call cannot be used to parallelize multiple processes (large-scale independent operations) within the code. To run the executable, open a command window and type the following:

../../_images/run_tdoctree.png

4.1.5.2. Setting Number of Threads with Open MPI

Before running the executable, the number of threads used to carry out all simultaneous processes can be set with Open MPI. This is set in the command window before running the executable. To set the number of threads (nThreads ), use the following syntax:

  • Windows computer: “set OMP_NUM_THREADS=nThreads”

  • Linux (bash shell): “export OMP_NUM_THREADS=nThreads”

  • Linux (csh shell): “setenv OMP_NUM_THREADS nThreads”

Important

The number of processes (nFreq ) times the number of threads (nThreads ) cannot exceed the total number of threads available from the computer.

4.1.5.3. Units

  • Electric field data: Ex, Ey and Ez in units V/m

  • Magnetic field data: Hx, Hy and Hz in units A/m.

  • Magnetic field data: dBx/dt, dBy/dt and -dBz/dt in units T/s. The vertical component of dB/dt is represented using -dBz/dt due to a long-standing plotting convention

  • Conductivity model: S/m

  • Susceptibility model: SI

  • Reference/starting conductivity model: S/m

  • Model/interface weights: unitless

Important

Any combination of data, electric and or magnetic field components, can be be inverted. A specified flag at the start of the observations file can be used to omit columns or individual datums.

4.1.5.4. Output Files

The program TDoctreeinv.exe creates the following output files:

  • dpred0.txt data predicted using the starting model or forward model

  • inv_xxx.con: recovered model at iteration ‘xxx’

  • dpred_xxx.txt data predicted using model ‘xxx’

  • inv.con: final conductivity model

  • tdoctree_v2.log: log file for the inversion

  • tdoctree_v2.out: stores details regarding the inversion