Difference in behavior between PYOPENCL_CTX and PYOPENCL_TEST

[matthiasdiener]

Describe the bug
Parsing of PYOPENCL_CTX and PYOPENCL_TEST is implemented differently, leading to a different selection behavior. An example is given below. #780 is another example.

To Reproduce

$ clinfo -l
Platform #0: AMD Accelerated Parallel Processing
 `-- Device #0: gfx90a:sramecc+:xnack-

$ PYOPENCL_TEST=AMD:90 python -c "import pyopencl; pyopencl.choose_devices()"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/p/lustre1/diener3/Work/enew/pyopencl/pyopencl/__init__.py", line 1561, in choose_devices
    for _plat, devs in get_test_platforms_and_devices():
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/p/lustre1/diener3/Work/enew/pyopencl/pyopencl/tools.py", line 646, in get_test_platforms_and_devices
    [find_cl_obj(devs, dev_id)
  File "/p/lustre1/diener3/Work/enew/pyopencl/pyopencl/tools.py", line 646, in <listcomp>
    [find_cl_obj(devs, dev_id)
     ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/p/lustre1/diener3/Work/enew/pyopencl/pyopencl/tools.py", line 618, in find_cl_obj
    return objs[num]
           ~~~~^^^^^
IndexError: list index out of range

$ PYOPENCL_CTX=AMD:90 python -c "import pyopencl; pyopencl.choose_devices()"
$ # works fine

Expected behavior
Having the same selection logic may be beneficial.

Environment (please complete the following information):

• OS: [e.g. Linux] Any
• ICD Loader and version: [e.g. ocl-icd 2.3.1] ocl-icd 2.3.2
• ICD and version: [e.g. pocl 1.8] Any
• CPU/GPU: [e.g. Nvidia Titan V] Any
• Python version: [e.g. 3.10] 3.11
• PyOpenCL version: [e.g. 2021.1] 2024.2.7

Additional context
Add any other context about the problem here.

[alexfikl]

The issue seems to be that the access to that objs array isn't guarded here:

pyopencl/pyopencl/tools.py

Line 618 in 846fede

return objs[num]

and the integer "90" in the "AMD:90" string matches that branch. The same-ish code in "choose_devices" is nicely guarded:

pyopencl/pyopencl/__init__.py

Lines 1640 to 1641 in 846fede

	if 0 <= int_choice < len(devices):
	return devices[int_choice]

Would probably be nice to unify that parsing 😁