Download correct CmdStan tarball on non-x86 linux (#616)

* Resolve download URL for non-x86 linux OSes

* Add doc

* Typo fix

* Refactor to avoid shell=True

* Fix CI issue

Author: WardBrian

.github/workflows/main.yml

@@ -39,7 +39,8 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        python-version: [3.7, 3.8, 3.9, "3.10"]
+        python-version: [3.7, 3.8, 3.9, "3.10.6"]
+        # more specific version of 3.10 due to https://github.com/python/mypy/issues/13627
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
     steps:

cmdstanpy/install_cmdstan.py

@@ -41,6 +41,7 @@
     validate_dir,
     wrap_url_progress_hook,
 )
+from cmdstanpy.utils.cmdstan import get_download_url
 
 from . import progress as progbar
 
@@ -426,10 +427,7 @@ def install_version(
 
 def is_version_available(version: str) -> bool:
     is_available = True
-    url = (
-        'https://github.com/stan-dev/cmdstan/releases/download/'
-        'v{0}/cmdstan-{0}.tar.gz'.format(version)
-    )
+    url = get_download_url(version)
     for i in range(6):
         try:
             urllib.request.urlopen(url)
@@ -458,10 +456,7 @@ def retrieve_version(version: str, progress: bool = True) -> None:
     if version is None or version == '':
         raise ValueError('Argument "version" unspecified.')
     print('Downloading CmdStan version {}'.format(version))
-    url = (
-        'https://github.com/stan-dev/cmdstan/releases/download/'
-        'v{0}/cmdstan-{0}.tar.gz'.format(version)
-    )
+    url = get_download_url(version)
     for i in range(6):  # always retry to allow for transient URLErrors
         try:
             if progress and progbar.allow_show_progress():

cmdstanpy/utils/cmdstan.py

@@ -3,6 +3,7 @@
 """
 import os
 import platform
+import subprocess
 import sys
 from collections import OrderedDict
 from typing import Callable, Dict, Optional, Tuple, Union
@@ -17,6 +18,46 @@
 EXTENSION = '.exe' if platform.system() == 'Windows' else ''
 
 
+def determine_linux_arch() -> str:
+    machine = platform.machine()
+    arch = ""
+    if machine == "aarch64":
+        arch = "arm64"
+    elif machine == "armv7l":
+        # Telling armel and armhf apart is nontrivial
+        # c.f. https://forums.raspberrypi.com/viewtopic.php?t=20873
+        readelf = subprocess.run(
+            ["readelf", "-A", "/proc/self/exe"],
+            check=True,
+            stdout=subprocess.PIPE,
+            text=True,
+        )
+        if "Tag_ABI_VFP_args" in readelf.stdout:
+            arch = "armel"
+        else:
+            arch = "armhf"
+    elif machine == "mips64":
+        arch = "mips64el"
+    elif machine == "ppc64el":
+        arch = "ppc64le"
+    elif machine == "s390x":
+        arch = "s390x"
+    return arch
+
+
+def get_download_url(version: str) -> str:
+    arch = os.environ.get("CMDSTAN_ARCH", "")
+    if not arch and platform.system() == "Linux":
+        arch = determine_linux_arch()
+
+    if arch and arch.lower() != "false":
+        url_end = f'v{version}/cmdstan-{version}-linux-{arch}.tar.gz'
+    else:
+        url_end = f'v{version}/cmdstan-{version}.tar.gz'
+
+    return f'https://github.com/stan-dev/cmdstan/releases/download/{url_end}'
+
+
 def validate_dir(install_dir: str) -> None:
     """Check that specified install directory exists, can write."""
     if not os.path.exists(install_dir):

docsrc/installation.rst

@@ -209,6 +209,17 @@ can be used to override these defaults:
     install_cmdstan -d my_local_cmdstan -v 2.27.0
     ls -F my_local_cmdstan
 
+Alternate Linux Architectures
+.............................
+
+CmdStan can be installed on Linux for the following non-x86 architectures:
+``arm64``, ``armel``, ``armhf``, ``mips64el``, ``ppc64el`` and ``s390x``.
+
+CmdStanPy will do its best to determine which of these is applicable for your
+machine when running ``install_cmdstan``. If the wrong choice is made, or if you
+need to manually override this, you can set the ``CMDSTAN_ARCH`` environment variable
+to one of the above options, or to "false" to use the standard x86 download.
+
 DIY Installation
 ^^^^^^^^^^^^^^^^