Update Windows installation instructions (#495)

* Update Windows installation instructions
* Explain ECHO ON usage
* Change wording of preamble
* Comments on flags

Author: joewallwork

pages/installation/systems.md

@@ -14,7 +14,8 @@ date: Last Updated: October 2025
 If possible we recommend using the [Windows Subsystem for Linux](https://learn.microsoft.com/en-us/windows/wsl/) (WSL) to build
 the library. In this case the build process is the same as for a Linux environment.
 
-To build in native Windows using Visual Studio and the Intel Fortran resources the following additional dependencies are required:
+Building in Windows itself can be done using Visual Studio and the Intel Fortran
+resources. The following additional dependencies are also required:
 
 * [Visual Studio](https://visualstudio.microsoft.com/) ensuring C++ tools are selected and installed.
 * [Intel OneAPI Basetoolkit](https://www.intel.com/content/www/us/en/developer/tools/oneapi/base-toolkit-download.html)
@@ -48,63 +49,83 @@ cmake --install .
 
 
 The following is an example `cmd` script that installs FTorch and runs the integration tests. It assumes you have already
-installed CMake, git, the Intel compilers, and Visual Studio.
+installed CMake, git, the Intel compilers, and Visual Studio. There are a few
+places where output is turned on or off using the `ECHO` command. If you are
+experiencing issues with the install then it may be helpful to set `ECHO ON`
+throughout.
 
 ```cmd
-rem disable output for now
-ECHO ON
+rem Disable output for now
+ECHO OFF
 
-rem load intel compilers
+rem Load intel compilers
 call "C:\Program Files (x86)\Intel\oneAPI\setvars.bat"
 
-rem download ftorch
+rem Download ftorch
 git clone https://github.com/Cambridge-ICCS/FTorch.git
 cd FTorch
 
-rem make venv
+rem Make virtual environment
 python -m venv .ftorch
 
-rem activate the environment
+rem Activate the virtual environment
 call .ftorch\Scripts\activate
 
-rem install torch
+rem Install torch
 pip install torch torchvision torchaudio
 
-rem enable output
+rem Enable output
 ECHO ON
 
-rem run cmake to generate build scripts
-rem (update CMAKE_PREFIX_PATH depending on location of ftorch venv)
+rem Find Torch location
+for /f "tokens=2*" %%i in ('pip show torch ^| findstr /R "^Location"') do set torch_path=%%i
+
+rem Run CMake to generate build scripts
+rem (Update CMAKE_PREFIX_PATH depending on location of ftorch venv)
 cmake -Bbuild -G "NMake Makefiles" -DCMAKE_Fortran_FLAGS="/fpscomp:logicals" ^
- -DCMAKE_PREFIX_PATH="C:\Users\Quickemu\Downloads\FTorch\.ftorch\Lib\site-packages" ^
+ -DCMAKE_PREFIX_PATH="%torch_path%" ^
  -DCMAKE_BUILD_TYPE=Release ^
  -DCMAKE_BUILD_TESTS=True ^
- -DCMAKE_Fortran_COMPILER=ifx -DCMAKE_C_COMPILER=icx -DCMAKE_CXX_COMPILER=icx
+ -DCMAKE_Fortran_COMPILER=ifx ^
+ -DCMAKE_C_COMPILER=icx ^
+ -DCMAKE_CXX_COMPILER=icx
+ -DCMAKE_Fortran_FLAGS="/fpscomp:logicals" ^
+ -DCMAKE_CXX_FLAGS="/D_ALLOW_COMPILER_AND_STL_VERSION_MISMATCH"
 
-rem build and install ftorch
+rem Build and install FTorch
 cmake --build build
 cmake --install build
 
-rem quit if this raises an error
+rem Quit if this raises an error
 if %errorlevel% neq 0 exit /b %errorlevel%
 
 ECHO OFF
-rem add ftorch and pytorch libs to path
-rem (update these depending on where you installed ftorch and where you created the venv)
-set PATH=C:\Users\Quickemu\Downloads\FTorch\.ftorch\Lib\site-packages;%PATH%
+rem Add FTorch and PyTorch libs to path
+rem (Update the first one depending on where you installed FTorch)
 set PATH=C:\Program Files (x86)\FTorch\bin;%PATH%
-set PATH=C:\Users\Quickemu\Downloads\FTorch\.ftorch\Lib\site-packages\torch\lib;%PATH%
+set PATH=%torch_path%;%PATH%
+set PATH=%torch_path%\torch\lib;%PATH%
 
-cd ..
-
-rem run integration tests
+rem Run integration tests
 ECHO ON
-run_integration_tests.bat
+ctest --verbose --tests-regex example1
+ctest --verbose --tests-regex example2
+ctest --verbose --tests-regex example3
+ctest --verbose --tests-regex example4
+ctest --verbose --tests-regex example8
 if %errorlevel% neq 0 exit /b %errorlevel%
 ```
 
-We recommend Windows users review the Windows CI workflow (`.github/workflows/test_suite_windows.yml`) for more
-information, as this provides another example of how to build and run FTorch and its integration tests.
+Here the `/fpscomp:logicals` flag is used to ensure Fortran logicals are
+compatible with those used by PyTorch. The
+`/D_ALLOW_COMPILER_AND_STL_VERSION_MISMATCH` flag is used to suppress warnings
+related to mismatched compiler versions between the Intel compilers and
+those used to build LibTorch.
+
+We recommend Windows users review the Windows continuous integration workflow
+([`.github/workflows/test_suite_windows_cpu_intel.yml`](https://github.com/Cambridge-ICCS/FTorch/blob/main/.github/workflows/test_suite_windows_cpu_intel.yml))
+for more information, as this provides another example of how to build and run
+FTorch and its integration tests.
 
 If using powershell the setvars and build commands become:
 ```