fix: correct nauty download URL and README improvements

- Fix nauty download URL: nauty29r3.tar.gz -> nauty2_9_3.tar.gz (404 fix)
- README: use dynamic brew --prefix path for Homebrew symlink example
- README: add -I /path/to/nauty to gcc compilation examples
- CI: add C4H10 test to Windows build for parity with other platforms

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: steinbeck

.github/workflows/build.yml

@@ -19,8 +19,8 @@ jobs:
 
       - name: Build nauty
         run: |
-          curl -L -o nauty29r3.tar.gz https://users.cecs.anu.edu.au/~bdm/nauty/nauty29r3.tar.gz
-          tar xzf nauty29r3.tar.gz
+          curl -L -o nauty2_9_3.tar.gz https://users.cecs.anu.edu.au/~bdm/nauty/nauty2_9_3.tar.gz
+          tar xzf nauty2_9_3.tar.gz
           cd nauty2_9_3
           ./configure && make
 
@@ -114,8 +114,8 @@ jobs:
 
       - name: Build nauty
         run: |
-          curl -L -o nauty29r3.tar.gz https://users.cecs.anu.edu.au/~bdm/nauty/nauty29r3.tar.gz
-          tar xzf nauty29r3.tar.gz
+          curl -L -o nauty2_9_3.tar.gz https://users.cecs.anu.edu.au/~bdm/nauty/nauty2_9_3.tar.gz
+          tar xzf nauty2_9_3.tar.gz
           cd nauty2_9_3
           ./configure && make
 
@@ -132,6 +132,7 @@ jobs:
         run: |
           ./surge.exe -help 2>&1 | head -3
           ./surge.exe -u C6H6
+          ./surge.exe -u C4H10
 
       - name: Upload Windows binary
         uses: actions/upload-artifact@v4

.github/workflows/release.yml

@@ -57,8 +57,8 @@ jobs:
       - name: Build nauty from source (Linux/Windows)
         if: matrix.os == 'ubuntu-latest' || matrix.os == 'windows-latest'
         run: |
-          curl -L -o nauty29r3.tar.gz https://users.cecs.anu.edu.au/~bdm/nauty/nauty29r3.tar.gz
-          tar xzf nauty29r3.tar.gz
+          curl -L -o nauty2_9_3.tar.gz https://users.cecs.anu.edu.au/~bdm/nauty/nauty2_9_3.tar.gz
+          tar xzf nauty2_9_3.tar.gz
           cd nauty2_9_3
           ./configure && make
 

Dockerfile

@@ -8,8 +8,8 @@ RUN apt-get update && \
 WORKDIR /build
 
 # Download and build nauty
-RUN curl -L -o nauty29r3.tar.gz https://users.cecs.anu.edu.au/~bdm/nauty/nauty29r3.tar.gz \
-    && tar xzf nauty29r3.tar.gz \
+RUN curl -L -o nauty2_9_3.tar.gz https://users.cecs.anu.edu.au/~bdm/nauty/nauty2_9_3.tar.gz \
+    && tar xzf nauty2_9_3.tar.gz \
     && cd nauty2_9_3 \
     && ./configure && make
 

README.md

@@ -84,22 +84,24 @@ make surge NAUTY=/path/to/nauty NAUTYLIB=/path/to/nauty
 ```
 Or compile directly with gcc:
 ```
-gcc -o surge -O3 -DWORDSIZE=64 -DMAXN=WORDSIZE -DOUTPROC=surgeproc \
-         -march=native -DPREPRUNE=surgepreprune \
+gcc -o surge -O3 -I /path/to/nauty -DWORDSIZE=64 -DMAXN=WORDSIZE \
+         -DOUTPROC=surgeproc -march=native -DPREPRUNE=surgepreprune \
          -DPRUNE=surgeprune -DGENG_MAIN=geng_main \
          surge.c geng.c planarity.c /path/to/nautyL1.a
 ```
 You can build-in gzip output using the zlib library (https://zlib.net). Add `-DZLIB` to the compilation, and link with the zlib library either by adding `-lz` or `libz.a`. This will activate the `-z` command to gzip the output:
 ```
-gcc -o surge -O3 -DWORDSIZE=64 -DMAXN=WORDSIZE -DOUTPROC=surgeproc \
-         -march=native -DPREPRUNE=surgepreprune -DZLIB \
-         -DPRUNE=surgeprune -DGENG_MAIN=geng_main \
+gcc -o surge -O3 -I /path/to/nauty -DWORDSIZE=64 -DMAXN=WORDSIZE \
+         -DOUTPROC=surgeproc -march=native -DPREPRUNE=surgepreprune \
+         -DZLIB -DPRUNE=surgeprune -DGENG_MAIN=geng_main \
          surge.c geng.c planarity.c /path/to/nautyL1.a -lz
 ```
 
 **Note for macOS Homebrew users:** If you installed nauty via Homebrew (`brew install nauty`), the library file may be named `libnautyL1.a` rather than `nautyL1.a`. You can create a symlink to make it work with the Makefile:
 ```
-ln -s /opt/homebrew/lib/libnautyL1.a /opt/homebrew/lib/nautyL1.a
+NAUTY_LIB=$(brew --prefix nauty)/lib
+ln -s "$NAUTY_LIB/libnautyL1.a" "$NAUTY_LIB/nautyL1.a"
+make surge NAUTY=$(brew --prefix nauty)/include/nauty NAUTYLIB=$(brew --prefix nauty)/lib
 ```
 
 ### Option 3: Use Docker