Hi,
When you observe a significant difference in execution speed between running a Fortran executable directly from the command line and calling it from MATLAB using the `system` command, several factors might be contributing to this discrepancy:
Potential Causes and Solutions
1. Environment Differences:
- Environment Variables: MATLAB might not inherit all the environment variables or settings that are available in your command line shell. This could affect the performance if your Fortran executable relies on specific environment settings for optimal performance.
- Path Differences: Ensure that any paths or dependencies required by the Fortran executable are correctly set when called from MATLAB.
2. Processor Affinity:
- Core Usage: The Fortran executable might be using different processor affinity settings when launched from MATLAB. You can try setting the processor affinity manually to ensure it uses all available cores.
- Parallel Execution: If your Fortran code uses OpenMP or other parallelization methods, make sure that the environment variables controlling threading are set appropriately within MATLAB.
3. MATLAB Overhead:
- MATLAB's Overhead: Running an executable from MATLAB can introduce some overhead due to the way MATLAB handles external processes. Although this shouldn't be significant, it might contribute to the observed delay.
- I/O Operations: If your Fortran executable performs file I/O operations, ensure that these files are accessible and that there are no additional delays caused by MATLAB's current working directory or file access permissions.
4. System Call Method:
- Asynchronous Execution: If possible, run the executable asynchronously and monitor its completion to reduce MATLAB's blocking time.
5. System Configuration:
- System Resources: Check if MATLAB's memory usage or other processes are affecting system performance when the executable is run from MATLAB.
Debugging Steps
1. Profile the Execution: Use MATLAB's profiling tools or external profiling tools to see where the time is being spent.
2. Log Outputs: Create logs for both command line and MATLAB executions to compare and identify any discrepancies in execution paths or errors.
3. Test in Isolated Environment: Run MATLAB with minimal startup options to ensure no additional toolboxes or settings are affecting performance.
By addressing these factors, you should be able to minimize the performance gap between running the executable directly and calling it from MATLAB.
Thank you.
