Simplifies cross platform installation setup.py (#3294)

# Description

This PR 

1. makes sure(skip if already satisfy, else install) the right torch is
installed before and after pip installing isaaclab packages as
sometime(rare case) due to flaky setup.py and unknown library
dependencies changes pytorch version gets overriden.

2. only install pink and retargeters in linux x86 or amd64 machines


## Type of change

<!-- As you go through the list, delete the ones that are not
applicable. -->

- Bug fix (non-breaking change which fixes an issue)

## Screenshots

Please attach before and after screenshots of the change if applicable.

<!--
Example:

| Before | After |
| ------ | ----- |
| _gif/png before_ | _gif/png after_ |

To upload images to a PR -- simply drag and drop an image while in edit
mode and it should upload the image directly. You can then paste that
source into the above before/after sections.
-->

## Checklist

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [x] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

<!--
As you go through the checklist above, you can mark something as done by
putting an x character in it

For example,
- [x] I have done this task
- [ ] I have not done this task
-->

---------
Co-authored-by: Mayank Mittal <12863862+Mayankm96@users.noreply.github.com>

isaaclab.bat

@@ -38,6 +38,33 @@ if not exist "%isaac_path%" (
 )
 goto :eof
 
+rem --- Ensure CUDA PyTorch helper ------------------------------------------
+:ensure_cuda_torch
+rem expects: !python_exe! set by :extract_python_exe
+setlocal EnableExtensions EnableDelayedExpansion
+set "TORCH_VER=2.7.0"
+set "TV_VER=0.22.0"
+set "CUDA_TAG=cu128"
+set "PYTORCH_INDEX=https://download.pytorch.org/whl/%CUDA_TAG%"
+
+rem Do we already have torch?
+call "!python_exe!" -m pip show torch >nul 2>&1
+if errorlevel 1 (
+    echo [INFO] Installing PyTorch !TORCH_VER! with CUDA !CUDA_TAG!...
+    call "!python_exe!" -m pip install "torch==!TORCH_VER!" "torchvision==!TV_VER!" --index-url "!PYTORCH_INDEX!"
+) else (
+    for /f "tokens=2" %%V in ('"!python_exe!" -m pip show torch ^| findstr /B /C:"Version:"') do set "TORCH_CUR=%%V"
+    echo [INFO] Found PyTorch version !TORCH_CUR!.
+    if /I not "!TORCH_CUR!"=="!TORCH_VER!+!CUDA_TAG!" (
+        echo [INFO] Replacing PyTorch !TORCH_CUR! -> !TORCH_VER!+!CUDA_TAG!...
+        call "!python_exe!" -m pip uninstall -y torch torchvision torchaudio >nul 2>&1
+        call "!python_exe!" -m pip install "torch==!TORCH_VER!" "torchvision==!TV_VER!" --index-url "!PYTORCH_INDEX!"
+    ) else (
+        echo [INFO] PyTorch !TORCH_VER!+!CUDA_TAG! already installed.
+    )
+)
+endlocal & exit /b 0
+
 rem -----------------------------------------------------------------------
 rem Returns success (exit code 0) if Isaac Sim's version starts with "4.5"
 rem -----------------------------------------------------------------------
@@ -334,23 +361,7 @@ if "%arg%"=="-i" (
     call :extract_python_exe
     rem check if pytorch is installed and its version
     rem install pytorch with cuda 12.8 for blackwell support
-    call !python_exe! -m pip list | findstr /C:"torch" >nul
-    if %errorlevel% equ 0 (
-        for /f "tokens=2" %%i in ('!python_exe! -m pip show torch ^| findstr /C:"Version:"') do (
-            set torch_version=%%i
-        )
-        if not "!torch_version!"=="2.7.0+cu128" (
-            echo [INFO] Uninstalling PyTorch version !torch_version!...
-            call !python_exe! -m pip uninstall -y torch torchvision torchaudio
-            echo [INFO] Installing PyTorch 2.7.0 with CUDA 12.8 support...
-            call !python_exe! -m pip install torch==2.7.0 torchvision==0.22.0 --index-url https://download.pytorch.org/whl/cu128
-        ) else (
-            echo [INFO] PyTorch 2.7.0 is already installed.
-        )
-    ) else (
-        echo [INFO] Installing PyTorch 2.7.0 with CUDA 12.8 support...
-        call !python_exe! -m pip install torch==2.7.0 torchvision==0.22.0 --index-url https://download.pytorch.org/whl/cu128
-    )
+    call :ensure_cuda_torch
 
     for /d %%d in ("%ISAACLAB_PATH%\source\*") do (
         set ext_folder="%%d"
@@ -372,6 +383,13 @@ if "%arg%"=="-i" (
     )
     rem install the rl-frameworks specified
     call !python_exe! -m pip install -e %ISAACLAB_PATH%\source\isaaclab_rl[!framework_name!]
+    rem in rare case if some packages or flaky setup override default torch installation, ensure right torch is
+    rem installed again
+    call :ensure_cuda_torch
+    rem update the vscode settings
+    rem once we have a docker container, we need to disable vscode settings
+    call :update_vscode_settings
+    shift
     shift
 ) else if "%arg%"=="--install" (
     rem install the python packages in source directory
@@ -379,23 +397,7 @@ if "%arg%"=="-i" (
     call :extract_python_exe
     rem check if pytorch is installed and its version
     rem install pytorch with cuda 12.8 for blackwell support
-    call !python_exe! -m pip list | findstr /C:"torch" >nul
-    if %errorlevel% equ 0 (
-        for /f "tokens=2" %%i in ('!python_exe! -m pip show torch ^| findstr /C:"Version:"') do (
-            set torch_version=%%i
-        )
-        if not "!torch_version!"=="2.7.0+cu128" (
-            echo [INFO] Uninstalling PyTorch version !torch_version!...
-            call !python_exe! -m pip uninstall -y torch torchvision torchaudio
-            echo [INFO] Installing PyTorch 2.7.0 with CUDA 12.8 support...
-            call !python_exe! -m pip install torch==2.7.0 torchvision==0.22.0 --index-url https://download.pytorch.org/whl/cu128
-        ) else (
-            echo [INFO] PyTorch 2.7.0 is already installed.
-        )
-    ) else (
-        echo [INFO] Installing PyTorch 2.7.0 with CUDA 12.8 support...
-        call !python_exe! -m pip install torch==2.7.0 torchvision==0.22.0 --index-url https://download.pytorch.org/whl/cu128
-    )
+    call :ensure_cuda_torch
 
     for /d %%d in ("%ISAACLAB_PATH%\source\*") do (
         set ext_folder="%%d"
@@ -417,6 +419,9 @@ if "%arg%"=="-i" (
     )
     rem install the rl-frameworks specified
     call !python_exe! -m pip install -e %ISAACLAB_PATH%\source\isaaclab_rl[!framework_name!]
+    rem in rare case if some packages or flaky setup override default torch installation, ensure right torch is
+    rem installed again
+    call :ensure_cuda_torch
     rem update the vscode settings
     rem once we have a docker container, we need to disable vscode settings
     call :update_vscode_settings

isaaclab.sh

@@ -96,6 +96,30 @@ is_docker() {
     [[ "$(hostname)" == *"."* ]]
 }
 
+ensure_cuda_torch() {
+  local py="$1"
+  local -r TORCH_VER="2.7.0"
+  local -r TV_VER="0.22.0"
+  local -r CUDA_TAG="cu128"
+  local -r PYTORCH_INDEX="https://download.pytorch.org/whl/${CUDA_TAG}"
+  local torch_ver
+
+  if "$py" -m pip show torch >/dev/null 2>&1; then
+    torch_ver="$("$py" -m pip show torch 2>/dev/null | awk -F': ' '/^Version/{print $2}')"
+    echo "[INFO] Found PyTorch version ${torch_ver}."
+    if [[ "$torch_ver" != "${TORCH_VER}+${CUDA_TAG}" ]]; then
+      echo "[INFO] Replacing PyTorch ${torch_ver} → ${TORCH_VER}+${CUDA_TAG}..."
+      "$py" -m pip uninstall -y torch torchvision torchaudio >/dev/null 2>&1 || true
+      "$py" -m pip install "torch==${TORCH_VER}" "torchvision==${TV_VER}" --index-url "${PYTORCH_INDEX}"
+    else
+      echo "[INFO] PyTorch ${TORCH_VER}+${CUDA_TAG} already installed."
+    fi
+  else
+    echo "[INFO] Installing PyTorch ${TORCH_VER}+${CUDA_TAG}..."
+    "$py" -m pip install "torch==${TORCH_VER}" "torchvision==${TV_VER}" --index-url "${PYTORCH_INDEX}"
+  fi
+}
+
 # extract isaac sim path
 extract_isaacsim_path() {
     # Use the sym-link path to Isaac Sim directory
@@ -364,21 +388,7 @@ while [[ $# -gt 0 ]]; do
             python_exe=$(extract_python_exe)
             # check if pytorch is installed and its version
             # install pytorch with cuda 12.8 for blackwell support
-            if ${python_exe} -m pip list 2>/dev/null | grep -q "torch"; then
-                torch_version=$(${python_exe} -m pip show torch 2>/dev/null | grep "Version:" | awk '{print $2}')
-                echo "[INFO] Found PyTorch version ${torch_version} installed."
-                if [[ "${torch_version}" != "2.7.0+cu128" ]]; then
-                    echo "[INFO] Uninstalling PyTorch version ${torch_version}..."
-                    ${python_exe} -m pip uninstall -y torch torchvision torchaudio
-                    echo "[INFO] Installing PyTorch 2.7.0 with CUDA 12.8 support..."
-                    ${python_exe} -m pip install torch==2.7.0 torchvision==0.22.0 --index-url https://download.pytorch.org/whl/cu128
-                else
-                    echo "[INFO] PyTorch 2.7.0 is already installed."
-                fi
-            else
-                echo "[INFO] Installing PyTorch 2.7.0 with CUDA 12.8 support..."
-                ${python_exe} -m pip install torch==2.7.0 torchvision==0.22.0 --index-url https://download.pytorch.org/whl/cu128
-            fi
+            ensure_cuda_torch ${python_exe}
             # recursively look into directories and install them
             # this does not check dependencies between extensions
             export -f extract_python_exe
@@ -404,6 +414,9 @@ while [[ $# -gt 0 ]]; do
             ${python_exe} -m pip install -e ${ISAACLAB_PATH}/source/isaaclab_rl["${framework_name}"]
             ${python_exe} -m pip install -e ${ISAACLAB_PATH}/source/isaaclab_mimic["${framework_name}"]
 
+            # in some rare cases, torch might not be installed properly by setup.py, add one more check here
+            # can prevent that from happening
+            ensure_cuda_torch ${python_exe}
             # check if we are inside a docker container or are building a docker image
             # in that case don't setup VSCode since it asks for EULA agreement which triggers user interaction
             if is_docker; then

source/isaaclab/setup.py

@@ -6,7 +6,6 @@
 """Installation script for the 'isaaclab' python package."""
 
 import os
-import platform
 import toml
 
 from setuptools import setup
@@ -47,12 +46,14 @@ INSTALL_REQUIRES = [
     "flaky",
 ]
 
-# Additional dependencies that are only available on Linux platforms
-if platform.system() == "Linux":
-    INSTALL_REQUIRES += [
-        "pin-pink==3.1.0",  # required by isaaclab.isaaclab.controllers.pink_ik
-        "dex-retargeting==0.4.6",  # required by isaaclab.devices.openxr.retargeters.humanoid.fourier.gr1_t2_dex_retargeting_utils
-    ]
+# Append Linux x86_64–only deps via PEP 508 markers
+X64 = "platform_machine in 'x86_64,AMD64'"
+INSTALL_REQUIRES += [
+    # required by isaaclab.isaaclab.controllers.pink_ik
+    f"pin-pink==3.1.0 ; platform_system == 'Linux' and ({X64})",
+    # required by isaaclab.devices.openxr.retargeters.humanoid.fourier.gr1_t2_dex_retargeting_utils
+    f"dex-retargeting==0.4.6 ; platform_system == 'Linux' and ({X64})",
+]
 
 PYTORCH_INDEX_URL = ["https://download.pytorch.org/whl/cu128"]