Bug with Python 3.8 and np.argmin

[larsoner]

Trying to compile some code on Python 3.8.0rc1 (what Ubuntu 19.10 ships with currently) and latest numpy (1.18.0.dev0+5ed0ebe) and numba (bdd8e31) master this code:

from numba import jit
import numpy as np


@jit(nopython=True)
def _bad():
    return np.argmin(np.zeros(1))

_bad()

Produces:

$ python -u numba38.py
/home/larsoner/python/numba/numba/dataflow.py:58: RuntimeWarning: inconsistent stack offset for block(offset:42, outgoing: [52], incoming: [24, 26])
  warnings.warn("inconsistent stack offset for %s" % blk,
...
File "numba38.py", line 7:
def _bad():
    return np.argmin(np.zeros(1))
    ^

[1] During: lowering "$0.7 = call $0.2($0.6, func=$0.2, args=[Var($0.6, numba38.py (7))], kws=(), vararg=None)" at numba38.py (7)

-------------------------------------------------------------------------------
This should not have happened, a problem has occurred in Numba's internals.
You are currently using Numba version 0.47.0dev0.

Full trace:

larsoner@bunk:~/Desktop$ python -u numba38.py 
/home/larsoner/python/numba/numba/dataflow.py:58: RuntimeWarning: inconsistent stack offset for block(offset:42, outgoing: [52], incoming: [24, 26])
  warnings.warn("inconsistent stack offset for %s" % blk,
Traceback (most recent call last):
  File "/home/larsoner/python/numba/numba/errors.py", line 717, in new_error_context
    yield
  File "/home/larsoner/python/numba/numba/lowering.py", line 260, in lower_block
    self.lower_inst(inst)
  File "/home/larsoner/python/numba/numba/lowering.py", line 303, in lower_inst
    val = self.lower_assign(ty, inst)
  File "/home/larsoner/python/numba/numba/lowering.py", line 465, in lower_assign
    return self.lower_expr(ty, value)
  File "/home/larsoner/python/numba/numba/lowering.py", line 927, in lower_expr
    res = self.lower_call(resty, expr)
  File "/home/larsoner/python/numba/numba/lowering.py", line 719, in lower_call
    res = self._lower_call_normal(fnty, expr, signature)
  File "/home/larsoner/python/numba/numba/lowering.py", line 898, in _lower_call_normal
    res = impl(self.builder, argvals, self.loc)
  File "/home/larsoner/python/numba/numba/targets/base.py", line 1132, in __call__
    res = self._imp(self._context, builder, self._sig, args, loc=loc)
  File "/home/larsoner/python/numba/numba/targets/base.py", line 1157, in wrapper
    return fn(*args, **kwargs)
  File "/home/larsoner/python/numba/numba/targets/arraymath.py", line 608, in array_argmin
    res = context.compile_internal(builder, array_argmin_impl, sig, args)
  File "/home/larsoner/python/numba/numba/targets/base.py", line 859, in compile_internal
    cres = self.compile_subroutine(builder, impl, sig, locals)
  File "/home/larsoner/python/numba/numba/targets/base.py", line 844, in compile_subroutine
    cres = self._compile_subroutine_no_cache(builder, impl, sig,
  File "/home/larsoner/python/numba/numba/targets/base.py", line 815, in _compile_subroutine_no_cache
    cres = compiler.compile_internal(self.typing_context, self,
  File "/home/larsoner/python/numba/numba/compiler.py", line 602, in compile_internal
    return pipeline.compile_extra(func)
  File "/home/larsoner/python/numba/numba/compiler.py", line 326, in compile_extra
    return self._compile_bytecode()
  File "/home/larsoner/python/numba/numba/compiler.py", line 385, in _compile_bytecode
    return self._compile_core()
  File "/home/larsoner/python/numba/numba/compiler.py", line 365, in _compile_core
    raise e
  File "/home/larsoner/python/numba/numba/compiler.py", line 356, in _compile_core
    pm.run(self.state)
  File "/home/larsoner/python/numba/numba/compiler_machinery.py", line 328, in run
    raise patched_exception
  File "/home/larsoner/python/numba/numba/compiler_machinery.py", line 319, in run
    self._runPass(idx, pass_inst, state)
  File "/home/larsoner/python/numba/numba/compiler_lock.py", line 32, in _acquire_compile_lock
    return func(*args, **kwargs)
  File "/home/larsoner/python/numba/numba/compiler_machinery.py", line 281, in _runPass
    mutated |= check(pss.run_pass, internal_state)
  File "/home/larsoner/python/numba/numba/compiler_machinery.py", line 268, in check
    mangled = func(compiler_state)
  File "/home/larsoner/python/numba/numba/untyped_passes.py", line 78, in run_pass
    func_ir = interp.interpret(bc)
  File "/home/larsoner/python/numba/numba/interpreter.py", line 103, in interpret
    self.dfa.run()
  File "/home/larsoner/python/numba/numba/dataflow.py", line 30, in run
    self.infos[blk.offset] = self.run_on_block(blk)
  File "/home/larsoner/python/numba/numba/dataflow.py", line 76, in run_on_block
    callback(info)
  File "/home/larsoner/python/numba/numba/dataflow.py", line 304, in pop_info
    info.pop()
  File "/home/larsoner/python/numba/numba/dataflow.py", line 853, in pop
    return self.make_incoming()
  File "/home/larsoner/python/numba/numba/dataflow.py", line 880, in make_incoming
    ib.request_outgoing(self, ret, stack_index)
  File "/home/larsoner/python/numba/numba/dataflow.py", line 897, in request_outgoing
    varname = self.stack[stack_index - self.stack_offset]
IndexError: Failed in nopython mode pipeline (step: analyzing bytecode)
list index out of range

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "numba38.py", line 9, in <module>
    _bad()
  File "/home/larsoner/python/numba/numba/dispatcher.py", line 420, in _compile_for_args
    raise e
  File "/home/larsoner/python/numba/numba/dispatcher.py", line 353, in _compile_for_args
    return self.compile(tuple(argtypes))
  File "/home/larsoner/python/numba/numba/compiler_lock.py", line 32, in _acquire_compile_lock
    return func(*args, **kwargs)
  File "/home/larsoner/python/numba/numba/dispatcher.py", line 768, in compile
    cres = self._compiler.compile(args, return_type)
  File "/home/larsoner/python/numba/numba/dispatcher.py", line 77, in compile
    status, retval = self._compile_cached(args, return_type)
  File "/home/larsoner/python/numba/numba/dispatcher.py", line 91, in _compile_cached
    retval = self._compile_core(args, return_type)
  File "/home/larsoner/python/numba/numba/dispatcher.py", line 104, in _compile_core
    cres = compiler.compile_extra(self.targetdescr.typing_context,
  File "/home/larsoner/python/numba/numba/compiler.py", line 528, in compile_extra
    return pipeline.compile_extra(func)
  File "/home/larsoner/python/numba/numba/compiler.py", line 326, in compile_extra
    return self._compile_bytecode()
  File "/home/larsoner/python/numba/numba/compiler.py", line 385, in _compile_bytecode
    return self._compile_core()
  File "/home/larsoner/python/numba/numba/compiler.py", line 365, in _compile_core
    raise e
  File "/home/larsoner/python/numba/numba/compiler.py", line 356, in _compile_core
    pm.run(self.state)
  File "/home/larsoner/python/numba/numba/compiler_machinery.py", line 328, in run
    raise patched_exception
  File "/home/larsoner/python/numba/numba/compiler_machinery.py", line 319, in run
    self._runPass(idx, pass_inst, state)
  File "/home/larsoner/python/numba/numba/compiler_lock.py", line 32, in _acquire_compile_lock
    return func(*args, **kwargs)
  File "/home/larsoner/python/numba/numba/compiler_machinery.py", line 281, in _runPass
    mutated |= check(pss.run_pass, internal_state)
  File "/home/larsoner/python/numba/numba/compiler_machinery.py", line 268, in check
    mangled = func(compiler_state)
  File "/home/larsoner/python/numba/numba/typed_passes.py", line 380, in run_pass
    NativeLowering().run_pass(state) # TODO: Pull this out into the pipeline
  File "/home/larsoner/python/numba/numba/typed_passes.py", line 325, in run_pass
    lower.lower()
  File "/home/larsoner/python/numba/numba/lowering.py", line 179, in lower
    self.lower_normal_function(self.fndesc)
  File "/home/larsoner/python/numba/numba/lowering.py", line 220, in lower_normal_function
    entry_block_tail = self.lower_function_body()
  File "/home/larsoner/python/numba/numba/lowering.py", line 245, in lower_function_body
    self.lower_block(block)
  File "/home/larsoner/python/numba/numba/lowering.py", line 260, in lower_block
    self.lower_inst(inst)
  File "/usr/lib/python3.8/contextlib.py", line 131, in __exit__
    self.gen.throw(type, value, traceback)
  File "/home/larsoner/python/numba/numba/errors.py", line 725, in new_error_context
    six.reraise(type(newerr), newerr, tb)
  File "/home/larsoner/python/numba/numba/six.py", line 669, in reraise
    raise value
numba.errors.LoweringError: Failed in nopython mode pipeline (step: nopython mode backend)
Failed in nopython mode pipeline (step: analyzing bytecode)
list index out of range

File "numba38.py", line 7:
def _bad():
    return np.argmin(np.zeros(1))
    ^

[1] During: lowering "$0.7 = call $0.2($0.6, func=$0.2, args=[Var($0.6, numba38.py (7))], kws=(), vararg=None)" at numba38.py (7)

-------------------------------------------------------------------------------
This should not have happened, a problem has occurred in Numba's internals.
You are currently using Numba version 0.47.0dev0.

Please report the error message and traceback, along with a minimal reproducer
at: https://github.com/numba/numba/issues/new

If more help is needed please feel free to speak to the Numba core developers
directly at: https://gitter.im/numba/numba

Thanks in advance for your help in improving Numba!

A more complicated version of this code works fine on Ubuntu 3.7.

Tagging #4071 since it's 3.8-related (I think).

[stuartarchibald]

Thanks for the report. Guessing solely from what is on stdout, the bytecode updates/changes in Python 3.8 are sufficiently altered that the current bytecode analysis is not working. We (core developers) anticipated this and are planning a 0.46.1 patch release to accommodate Python 3.8.

[ulijh]

This works with the current master. Could be closed I guess.

[esc]

@ulijh thanks for circling back on this and confirming that it does work on master. I am assuming this is the result of #4755 being merged. Closing now.

[larsoner]

Indeed things appear fixed on 3.8 for me on master, thanks!