Libtorch regression example (#213)

* Sketch libtorch test

* Readme for libtorch example

* cppstd 17

* Testing

* It's gnu...

* It's gnu..., but not in windows!

* DOn't build for windows

* Use update

---------

Co-authored-by: Carlos Zoido <mrgalleta@gmail.com>

Author: AbrilRBS

examples/libraries/README.md

@@ -9,3 +9,5 @@
 ### [Using libcurl to download an image and stb to read it](libcurl/download_image)
 
 ### [Using libcurl to download an image and stb to read it (color version with fmt)](libcurl/ascii_art_color)
+
+### [Using libtorch](libtorch/regression)

examples/libraries/libtorch/regression/README.md

@@ -0,0 +1,22 @@
+## Libtorch example with Conan
+
+This example shows how to use Libtorch with Conan package manager to build a simple regression model.
+
+The regression source code is not hosted in this repository,
+we use [the official PyTorch examples repository](https://github.com/pytorch/examples/tree/main/cpp/regression),
+so make sure to clone it first and then navigate to the `cpp/regression` folder:
+
+```bash
+$ git clone https://github.com/pytorch/examples/tree/main/cpp/regression
+$ cd cpp/regression
+```
+
+Then, copy the `conanfile.txt` from this directory to the `cpp/regression` folder,
+and finally run Conan and CMake as usual:
+
+```bash
+$ conan install --build=missing
+$ cmake --preset conan-release  # conan-default for Windows
+$ cmake --build --preset conan-release
+$ ./build/Release/regression
+```

examples/libraries/libtorch/regression/ci_test_example.py

@@ -0,0 +1,26 @@
+import platform
+import shutil
+
+from test.examples_tools import run, chdir
+
+print("Libtorch regression example with Conan")
+
+run("git clone --depth 1 https://github.com/pytorch/examples.git")
+shutil.copy("conanfile.txt", "examples/cpp/regression/conanfile.txt")
+
+with chdir("examples/cpp/regression"):
+    cppstd = "17" if platform.system() == "Windows" else "gnu17"
+    run(f"conan install -b=missing -s compiler.cppstd={cppstd} --update")
+
+    if platform.system() == "Windows":
+        run("cmake --preset conan-default")
+        # Don't build on Windows. CI's msvc can't build this
+    else:
+        run("cmake --preset conan-release")
+        run("cmake --build --preset conan-release")
+
+    # Only execute this in macos in the CI, there are some issues with the generated binary and the
+    # GitHub images
+    if platform.system() == "Darwin":
+        run("./build/Release/regression")
+

examples/libraries/libtorch/regression/conanfile.txt

@@ -0,0 +1,9 @@
+[requires]
+libtorch/[*]
+
+[generators]
+CMakeToolchain
+CMakeDeps
+
+[layout]
+cmake_layout