test_geod_inverse_transform fails on 64bit PowerPC architectures

[sebastic]

The Debian package build for 3.1rc0 failed on 64bit PowerPC architectures:

https://buildd.debian.org/status/package.php?p=python-pyproj&suite=experimental

From the ppc64el buildlog:

=================================== FAILURES ===================================
_________________________ test_geod_inverse_transform __________________________

    def test_geod_inverse_transform():
        gg = Geod(ellps="clrk66")
        lat1pt = 42.0 + (15.0 / 60.0)
        lon1pt = -71.0 - (7.0 / 60.0)
        lat2pt = 45.0 + (31.0 / 60.0)
        lon2pt = -123.0 - (41.0 / 60.0)
        """
        distance between boston and portland, clrk66:
        -66.531 75.654  4164192.708
        distance between boston and portland, WGS84:
        -66.530 75.654  4164074.239
        testing pickling of Geod instance
        distance between boston and portland, clrk66 (from pickle):
        -66.531 75.654  4164192.708
        distance between boston and portland, WGS84 (from pickle):
        -66.530 75.654  4164074.239
        inverse transform
        from proj.4 invgeod:
        b'-66.531\t75.654\t4164192.708\n'
    
        """
        true_az12 = -66.5305947876623
        true_az21 = 75.65363415556968
        print("from pyproj.Geod.inv:")
        az12, az21, dist = gg.inv(lon1pt, lat1pt, lon2pt, lat2pt)
        assert_almost_equal(
            (az12, az21, dist), (true_az12, true_az21, 4164192.708), decimal=3
        )
    
        print("forward transform")
        print("from proj.4 geod:")
        endlon, endlat, backaz = gg.fwd(lon1pt, lat1pt, az12, dist)
        assert_almost_equal(
            (endlon, endlat, backaz), (lon2pt, lat2pt, true_az21), decimal=3
        )
    
        inc_exc = ["excluding", "including"]
        res_az12_az21_dists_all = [
            (180.0, 0.0, 0.0),
            (-66.53059478766238, 106.79071710136431, 832838.5416198927),
            (-73.20928289863558, 99.32289055927389, 832838.5416198935),
            (-80.67710944072617, 91.36325611787134, 832838.5416198947),
            (-88.63674388212858, 83.32809401477382, 832838.5416198922),
            (-96.67190598522616, 75.65363415556973, 832838.5416198926),
        ]
        point_count = len(res_az12_az21_dists_all)
        for include_initial, include_terminus in itertools.product(
            (False, True), (False, True)
        ):
            initial_idx = int(not include_initial)
            terminus_idx = int(not include_terminus)
    
            npts = point_count - initial_idx - terminus_idx
            print("intermediate points:")
            print("from geod with +lat_1,+lon_1,+lat_2,+lon_2,+n_S:")
            print(f"{lat1pt:6.3f} {lon1pt:7.3f} {lat2pt:6.3f} {lon2pt:7.3f} {npts}")
    
            lonlats = gg.npts(
                lon1pt,
                lat1pt,
                lon2pt,
                lat2pt,
                npts,
                initial_idx=initial_idx,
                terminus_idx=terminus_idx,
            )
            assert len(lonlats) == npts
    
            npts1 = npts + initial_idx + terminus_idx - 1
            del_s = dist / npts1
            print(
                f"Total distnace is {dist}, "
                f"Points count: {npts}, "
                f"{inc_exc[include_initial]} initial point, "
                f"{inc_exc[include_terminus]} terminus point. "
                f"The distance between successive points is {dist}/{npts1} = {del_s}"
            )
    
            from_idx = initial_idx
            to_idx = point_count - terminus_idx
            res_az12_az21_dists = res_az12_az21_dists_all[from_idx:to_idx]
    
            lonprev = lon1pt
            latprev = lat1pt
            for (lon, lat), (res12, res21, resdist) in zip(lonlats, res_az12_az21_dists):
                o_az12, o_az21, o_dist = gg.inv(lonprev, latprev, lon, lat)
>               assert_almost_equal((o_az12, o_az21, o_dist), (res12, res21, resdist))
E               AssertionError: 
E               Arrays are not almost equal to 7 decimals
E               
E               Mismatched elements: 2 / 3 (66.7%)
E               Max absolute difference: 180.
E               Max relative difference: 1.
E                x: array([0.0000000e+00, 1.8000000e+02, 9.0976802e-10])
E                y: array([180.,   0.,   0.])

test/test_geod.py:135: AssertionError
----------------------------- Captured stdout call -----------------------------
from pyproj.Geod.inv:
forward transform
from proj.4 geod:
intermediate points:
from geod with +lat_1,+lon_1,+lat_2,+lon_2,+n_S:
42.250 -71.117 45.517 -123.683 4
Total distnace is 4164192.7080994667, Points count: 4, excluding initial point, excluding terminus point. The distance between successive points is 4164192.7080994667/5 = 832838.5416198934
intermediate points:
from geod with +lat_1,+lon_1,+lat_2,+lon_2,+n_S:
42.250 -71.117 45.517 -123.683 5
Total distnace is 4164192.7080994667, Points count: 5, excluding initial point, including terminus point. The distance between successive points is 4164192.7080994667/5 = 832838.5416198934
intermediate points:
from geod with +lat_1,+lon_1,+lat_2,+lon_2,+n_S:
42.250 -71.117 45.517 -123.683 5
Total distnace is 4164192.7080994667, Points count: 5, including initial point, excluding terminus point. The distance between successive points is 4164192.7080994667/5 = 832838.5416198934
=============================== warnings summary ===============================
.pybuild/cpython3_3.9_pyproj/build/test/test_datadir.py::test_get_data_dir__from_user[str]
.pybuild/cpython3_3.9_pyproj/build/test/test_datadir.py::test_get_data_dir__from_user[Path]
.pybuild/cpython3_3.9_pyproj/build/test/test_datadir.py::test_append_data_dir__internal[str]
.pybuild/cpython3_3.9_pyproj/build/test/test_datadir.py::test_append_data_dir__internal[Path]
  /<<PKGBUILDDIR>>/.pybuild/cpython3_3.9_pyproj/build/pyproj/datadir.py:37: UserWarning: pyproj unable to set database path.
    _global_context_set_data_dir()

-- Docs: https://docs.pytest.org/en/stable/warnings.html
=========================== short test summary info ============================
FAILED test/test_geod.py::test_geod_inverse_transform - AssertionError: 
= 1 failed, 719 passed, 3 skipped, 59 deselected, 4 warnings in 162.11s (0:02:42) =

[snowman2]

Thanks for the report @sebastic 👍

Likely related to #841

ping @idanmiara in case you have any ideas.

[idanmiara]

Thanks for the report @sebastic 👍

Likely related to #841

ping @idanmiara in case you have any ideas.

I think it fails when comparing the az from the initial point to the first point in the result array, which is also the initial point. So it could be 0 or 180 or any other number.
I'll modify that test to fix it.