provide a better error message when no platforms found (#826)

* provide a better error message when no platforms found

* Add link, improve phrasing

---------

Co-authored-by: Andreas Klöckner <[email protected]>

Author: matthiasdiener

pyopencl/__init__.py

@@ -1597,7 +1597,21 @@ def get_input(prompt):
 
     # {{{ pick a platform
 
-    platforms = get_platforms()
+    try:
+        platforms = get_platforms()
+    except LogicError as e:
+        if "PLATFORM_NOT_FOUND_KHR" in str(e):
+            # With the cl_khr_icd extension, clGetPlatformIDs fails if no platform
+            # is available:
+            # https://registry.khronos.org/OpenCL/sdk/3.0/docs/man/html/clGetPlatformIDs.html
+            raise RuntimeError("no CL platforms available to ICD loader. "
+                               "Install a CL driver "
+                               "('ICD', such as pocl, rocm, Intel CL) to fix this. "
+                               "See pyopencl docs for help: "
+                               "https://documen.tician.de/pyopencl/"
+                               "misc.html#installation") from e
+        else:
+            raise
 
     if not platforms:
         raise Error("no platforms found")

pyproject.toml

@@ -14,6 +14,7 @@ name = "pyopencl"
 version = "2025.1"
 description = "Python wrapper for OpenCL"
 readme = "README.rst"
+license = "MIT"
 authors = [
     { name = "Andreas Kloeckner", email = "[email protected]" },
 ]
@@ -24,7 +25,6 @@ classifiers = [
     "Intended Audience :: Developers",
     "Intended Audience :: Other Audience",
     "Intended Audience :: Science/Research",
-    "License :: OSI Approved :: MIT License",
     "Natural Language :: English",
     "Programming Language :: C++",
     "Programming Language :: Python",