$x .= $x->index(...) leads to "Not physical but doesn't have parent at ufunc.pd" when used later

[djerius]

Howdy,

The following code used to work back in the day (2.016?), but now fails.

Loaded PDL v2.084 (supports bad values)
pdl> $x = sequence(1000)

pdl> $idx = random( $x->nelem) * $nelem

pdl> $x .= $x->index($idx);

pdl> p $x->min
PDL Not physical but doesn't have parent at ufunc.pd line 564.
        PDL::min(PDL=SCALAR(0x1fffdc8)) called at (eval 218) line 4
        main::__ANON__() called at /home/dj/.plenv/x86_64-linux_RHEL-8/versions/5.38-mst/bin/perldl line 682
        eval {...} called at /home/dj/.plenv/x86_64-linux_RHEL-8/versions/5.38-mst/bin/perldl line 682
        main::eval_and_report("p \$x->min\x{a}") called at /home/dj/.plenv/x86_64-linux_RHEL-8/versions/5.38-mst/bin/perldl line 618
        main::process_input() called at /home/dj/.plenv/x86_64-linux_RHEL-8/versions/5.38-mst/bin/perldl line 638
        eval {...} called at /home/dj/.plenv/x86_64-linux_RHEL-8/versions/5.38-mst/bin/perldl line 638

[mohawk2]

I just tried this with latest master. It worked fine. Can you confirm which version of PDL you tried this with?

[mohawk2]

The error shown did happen while I was fixing the DATACHANGED propagation, and was caused by that being propagated to the output (aka child) of a non-flowing operation (like here, .= aka assgn). The fix was to not propagate to non-flowing output transes:

pdl/Basic/Core/pdlapi.c

Line 870 in 0e4e6cb

if (!(trans->flags & PDL_ITRANS_DO_DATAFLOW_F)) continue;

That worked because make_physical shortcuts if the ndarray doesn't have DATACHANGED set, as there's nothing to do.

[mohawk2]

You can prove this yourself by updating to the latest master, which includes the test you show here, and deleting line 870 of pdlapi.c, as I just tried, and seeing the test fail, as I just saw. It looks like you are reporting a bug that doesn't exist. Please be careful about that.