Linux Compatibility Assessment for GULF Model

The GULF model can successfully run on Linux systems, but migrating from Windows requires addressing several compatibility challenges and using alternative versions of some components. Here's a comprehensive implementation guide based on detailed research.

Executive Summary

The GULF model's core components have strong Linux support through official USGS channels, but the specific versions mentioned (MODFLOW 6 v6.2.1 and PEST++ v5.1.0) are not available as pre-compiled Linux binaries. Modern alternatives and source compilation options provide viable pathways for Linux deployment, though manual script conversion and some version updates will be required.

1. Core Software Compatibility

MODFLOW 6 Linux Availability

Status: Compatible with version constraints

The MODFLOW 6 v6.2.1 specifically is not available as a pre-compiled Linux binary in current USGS releases. However, Linux compatibility is excellent through multiple pathways:

• Current available versions: 6.4.4 through 6.6.2 with full Linux support
• Official Linux binaries: Available through USGS GitHub releases (MODFLOW-ORG/executables)
• Built on Ubuntu 20.04: Ensures broad Linux distribution compatibility
• Installation methods: Pre-compiled binaries, FloPy's get-modflow utility, or source compilation

Recommendation: Use MODFLOW 6 v6.4.4+ which includes all v6.2.1 functionality plus improvements, or compile v6.2.1 from historical source code if the specific version is critical.

PEST++ Linux Availability

Status: Compatible with version adjustment

PEST++ v5.1.0 is not available as a pre-compiled binary, but Linux support exists:

• Available version: PEST++ v5.0.0 includes official Linux binaries
• Source compilation: Full C++ source code available with CMake build system
• Self-contained: No external dependencies required
• Installation: mkdir build && cd build && cmake .. && make -j$(nproc)

Recommendation: Use PEST++ v5.0.0 official release or compile v5.1.0 from source code.

2. Python Environment Compatibility

Confirmed Linux-Compatible Packages

Status: Fully compatible

• flopy: Excellent Linux support with automatic MODFLOW executable management
• pyemu: Full Linux compatibility with extensive USGS Linux usage
• Installation: conda install -c conda-forge flopy pyemu or pip install flopy pyemu

Unresolved Package: spnspecs

Status: Package not found

Research could not identify "spnspecs" as a standalone Python package. This may be:

• An internal module within the GULF model codebase
• Specification files rather than a Python package
• A misidentified or legacy package name

Action required: Verify the correct package name with GULF model developers or check if this functionality is incorporated into flopy/pyemu.

3. Script Conversion Requirements

Batch Script to Shell Script Conversion

Status: Manual conversion required

No reliable automated tools exist for converting Windows batch scripts to Linux shell scripts. Manual conversion is necessary using established patterns:

Key conversion patterns:

• Variables: %VAR% → $VAR
• Paths: \ → /
• Commands: DIR → ls -l, COPY → cp, DEL → rm
• Conditionals: IF %VAR%==value → if [ "$VAR" = "value" ]

Example conversion:

# Windows batch
@echo off
cd /d %~dp0
mf6.exe model.nam
if errorlevel 1 goto error
echo Model completed successfully

# Linux shell
#!/bin/bash
cd "$(dirname "$0")"
./mf6 model.nam
if [ $? -ne 0 ]; then
    echo "Model run failed"
    exit 1
fi
echo "Model completed successfully"

7-Zip Replacement

Status: Direct alternatives available

p7zip provides the closest equivalent to 7z.exe:

• Installation: sudo apt install p7zip-full (Ubuntu/Debian)
• Commands: 7z a archive.7z files/ and 7z x archive.7z
• Alternative: Official 7-Zip for Linux (7zz command) for latest features

GUI alternatives: PeaZip for comprehensive archive management with graphical interface.

4. Implementation Steps

Phase 1: Environment Setup

1. Install Linux system: Ubuntu 20.04 LTS or 22.04 LTS recommended
2. Install Python environment: conda create -n gulf-model python=3.10
3. Install packages: conda install -c conda-forge flopy pyemu
4. Install archive tools: sudo apt install p7zip-full

Phase 2: Software Installation

1. MODFLOW 6: Use get-modflow command or download from USGS releases
2. PEST++: Download v5.0.0 Linux binaries or compile from source
3. Verify installations: Test executables run without errors

Phase 3: Script Migration

1. Analyze existing batch scripts to understand workflow
2. Convert manually using command mapping tables
3. Test thoroughly on Linux system
4. Handle path and file system differences

Phase 4: Model Testing

1. Run small test cases to verify functionality
2. Compare results with Windows version for validation
3. Document any remaining issues for resolution

5. Potential Challenges and Solutions

Version Compatibility Issues

Challenge: Specific software versions unavailable Solution: Use newer versions with backward compatibility or compile from source

Unknown Python Package

Challenge: spnspecs package not found Solution: Contact GULF model developers or check if functionality exists in other packages

Script Complexity

Challenge: Complex batch scripts may have Windows-specific dependencies Solution: Consider rewriting in Python using flopy for better cross-platform compatibility

Performance Differences

Challenge: Different compiler optimizations between Windows and Linux Solution: Use Intel compilers if available, or optimize GCC compilation flags

6. Recommended Implementation Path

For Standard Users

1. Use newer software versions (MODFLOW 6 v6.4.4+, PEST++ v5.0.0)
2. Install via package managers (conda-forge preferred)
3. Convert scripts manually using provided conversion tables
4. Test incrementally with simple cases first

For Advanced Users

1. Compile specific versions from source code if required
2. Use containerization (Docker) for consistent deployment
3. Implement parallel processing for large-scale simulations
4. Consider HPC integration for computational efficiency

7. Success Probability and Timeline

Feasibility: High - All core components have Linux support through official channels Implementation time: 2-4 weeks for complete migration including testing Key dependencies: Resolving spnspecs package and thorough script conversion

The GULF model can successfully run on Linux systems with proper planning and implementation of these compatibility measures. The strong official support for MODFLOW 6 and PEST++ on Linux, combined with established conversion methodologies, provides a clear path forward for Linux deployment.