1 files changed, 100 insertions, 0 deletions
diff --git a/examples/poiseulle_particles_2d_compare/.nix/derivation.nix b/examples/poiseulle_particles_2d_compare/.nix/derivation.nix
index 415bd6a..de2d415 100644
--- a/examples/poiseulle_particles_2d_compare/.nix/derivation.nix
+++ b/examples/poiseulle_particles_2d_compare/.nix/derivation.nix
@@ -1,3 +1,103 @@
 { lib
 , stdenv
+, python3
 }:
+
+{ pkgs ? import <nixpkgs> {} }:
+
+let
+
+  pythonEnv = python3.withPackages (ps: with ps; [
+    pandas
+    matplotlib
+    numpy
+    imageio        # for video output
+    imageio-ffmpeg # ffmpeg backend for imageio
+  ]);
+
+  # The comparison & video generation script (embedded)
+  compareAndRenderPy = pkgs.writeText "compare_and_render.py" ''
+    import pandas as pd
+    import matplotlib.pyplot as plt
+    import numpy as np
+    import argparse
+    import os
+    import imageio.v2 as iio
+    from matplotlib.animation import FuncAnimation, FFMpegWriter
+
+    def main():
+        parser = argparse.ArgumentParser()
+        parser.add_argument('--csv1', required=True)
+        parser.add_argument('--csv2', required=True)
+        parser.add_argument('--csv3', required=True)
+        parser.add_argument('--video-dir', required=True)
+        args = parser.parse_args()
+
+        df1 = pd.read_csv(args.csv1)
+        df2 = pd.read_csv(args.csv2)
+        df3 = pd.read_csv(args.csv3)
+
+        times = df1['time'].values
+        fig, (ax1, ax2) = plt.subplots(2, 1, figsize=(10, 8))
+
+        def update(frame):
+            ax1.clear()
+            ax2.clear()
+            ax1.set_title(f'Velocity at t = {times[frame]:.2f}')
+            ax2.set_title(f'Pressure at t = {times[frame]:.2f}')
+            ax1.plot(times[:frame+1], df1['velocity'][:frame+1], label='Binary1')
+            ax1.plot(times[:frame+1], df2['velocity'][:frame+1], label='Binary2')
+            ax1.plot(times[:frame+1], df3['velocity'][:frame+1], label='Binary3')
+            ax2.plot(times[:frame+1], df1['pressure'][:frame+1], label='Binary1')
+            ax2.plot(times[:frame+1], df2['pressure'][:frame+1], label='Binary2')
+            ax2.plot(times[:frame+1], df3['pressure'][:frame+1], label='Binary3')
+            ax1.legend(), ax2.legend()
+            ax1.set_xlim(times[0], times[-1])
+            ax2.set_xlim(times[0], times[-1])
+
+        ani = FuncAnimation(fig, update, frames=len(times), repeat=False)
+        writer = FFMpegWriter(fps=5, bitrate=1800)
+        os.makedirs(args.video_dir, exist_ok=True)
+        video_path = os.path.join(args.video_dir, 'comparison.mp4')
+        ani.save(video_path, writer=writer)
+        print(f"Video saved to {video_path}")
+
+    if __name__ == '__main__':
+        main()
+  '';
+
+  # Wrapper script that runs the three binaries and then the Python comparison
+  runScript = pkgs.writeShellScript "run-simulation-pipeline" ''
+    set -e
+    mkdir -p results videos
+
+    echo "Running binary1..."
+    ${binary1}/bin/sim1
+    echo "Running binary2..."
+    ${binary2}/bin/sim2
+    echo "Running binary3..."
+    ${binary3}/bin/sim3
+
+    echo "Generating comparison video..."
+    ${pythonEnv}/bin/python ${compareAndRenderPy} \
+      --csv1 results/binary1.csv \
+      --csv2 results/binary2.csv \
+      --csv3 results/binary3.csv \
+      --video-dir videos
+
+    echo "Done. Video available at videos/comparison.mp4"
+  '';
+
+in
+pkgs.stdenv.mkDerivation {
+  name = "simulation-pipeline";
+  buildInputs = [ hlbm_2d psm_2d bgk_2d pythonEnv pkgs.ffmpeg ]; # ffmpeg for video encoding
+  buildCommand = ''
+    mkdir -p $out/bin
+    cp ${runScript} $out/bin/run-pipeline
+    chmod +x $out/bin/run-pipeline
+    # Optionally copy the Python script for reference
+    cp ${compareAndRenderPy} $out/compare_and_render.py
+    echo "Pipeline installed. Run $out/bin/run-pipeline"
+  '';
+}