add irregular_waves.cpp checks and update irregular wave consistency plot

- Add empty data checks after reading eta file
- Change ExcitationConvolution to skip (not throw) when time exceeds precomputed range at end of simulation
- Simplify irregular wave consistency test postprocessing script

Author: dav-og

src/hydro/waves/irregular_wave.cpp

@@ -41,6 +41,13 @@ void IrregularWaves::InitializeIRFVectors() {
     if (!params_.eta_file_path_.empty()) {
         ReadEtaFromFile();
 
+        // Check if eta file was read successfully
+        if (time_data_.empty() || free_surface_elevation_sampled_.empty()) {
+            std::cerr << "Error: Failed to read eta data from file: " << params_.eta_file_path_ << std::endl;
+            spectrumCreated_ = false;
+            return;
+        }
+        
         // Populate free_surface_time_sampled_ from time_data_, extending backwards
         // to cover negative times needed for IRF convolution (same as CreateFreeSurfaceElevation does)
         double t_irf_max = 0.0;
@@ -397,11 +404,10 @@ double IrregularWaves::ExcitationConvolution(int body, int dof, double time) {
             f_ex += irf_val_mat(dof, j) * eta_val * irf_width_array[j];
 
         } else {
-            throw std::runtime_error(
-                "Excitation convolution: trying to find free surface elevation at a time out of bounds from the "
-                "precomputed free surface elevation (" +
-                std::to_string(t_tau) + "not in [" + std::to_string(tmin) + ", " + std::to_string(tmax) +
-                "]). Excitation force ignored at this time step.");
+            // Time is outside precomputed range - skip this convolution term.
+            // This can happen at the very end of simulation when time slightly exceeds
+            // the simulation duration due to timestep discretization.
+            continue;
         }
     }
 

tests/regression/sphere/compare_sphere_irreg_waves_eta_consistency.py

@@ -13,10 +13,11 @@
 import sys
 import os
 from pathlib import Path
+import numpy as np
 
 # Import the comparison template
 sys.path.append(os.path.join(os.path.dirname(__file__), '../utilities'))
-from compare_template import run_consistency_comparison
+from compare_template import create_comparison_plot, format_path
 
 if __name__ == '__main__':
     """
@@ -42,17 +43,34 @@
 
     # Test-specific configuration
     test_name = "Sphere Irreg Waves Eta Consistency"
-    safe_test_name = test_name.lower().replace(' ', '_').replace('-', '_')
-    print(f"Plot filename: {plots_dir}/{safe_test_name}_comparison.png")
     y_label = "Heave (m)"
     tolerance = 1e-6
+
+    # Load the results file (columns: time, heave_spectrum, heave_eta, diff)
+    # Skip header lines (title + separator)
+    data = np.loadtxt(fname_rst, skiprows=2)
+    
+    # Extract columns as ref (spectrum) and test (eta) data for comparison
+    ref_data = np.column_stack((data[:, 0], data[:, 1]))   # time, spectrum
+    test_data = np.column_stack((data[:, 0], data[:, 2]))  # time, eta
 
-    # Run the consistency comparison using the template
-    max_diff, passed = run_consistency_comparison(
-        fname_rst, test_name, y_label,
-        tolerance=tolerance,
-        ref_label="Spectrum",
-        sim_label="Eta-Import"
+    print(f"Loaded {len(data)} data points")
+
+    # Generate comparison plot using standard template
+    n1, n2 = create_comparison_plot(
+        ref_data, test_data, test_name, plots_dir,
+        ref_file_path=format_path(fname_rst),
+        test_file_path=format_path(fname_rst),
+        y_label=y_label
     )
+
+    # Check pass/fail
+    max_diff = np.max(np.abs(data[:, 3]))  # Use pre-computed diff column
+    passed = max_diff < tolerance
+    
+    if passed:
+        print(f"TEST PASSED - Max difference: {max_diff:.2e}, Tolerance: {tolerance:.2e}")
+    else:
+        print(f"TEST FAILED - Max difference: {max_diff:.2e} exceeds tolerance: {tolerance:.2e}")
 
     sys.exit(0 if passed else 1)