Cannot coerce to or from object in nopython contex

Question

Following up from here, Numba is finally working (after weeks) on my machine, without any weird indentation errors.

I've implemented it as in the solution to the linked question.

However, I now get this string of errors from Numba, the last line being that it can't coerce to or from object in nopython context:

Traceback (most recent call last):
  File "C:\Users\app\Documents\Python Scripts\gbc_classifier_train.py", line 19, in <module>
    import gentleboost_c_class_jit_v6_nolimit as gbc
  File "C:\Users\app\Documents\Python Scripts\gentleboost_c_class_jit_v6_nolimit.py", line 26, in <module>
    @jit(void(object_, float_[:,:], int_[:], int_))
  File "C:\Users\app\Anaconda\lib\site-packages\numba\decorators.py", line 224, in _jit_decorator
    nopython=nopython, func_ast=func_ast, **kwargs)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\decorators.py", line 133, in compile_function
    func_env = pipeline.compile2(env, func, restype, argtypes, func_ast=func_ast, **kwds)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\pipeline.py", line 144, in compile2
    post_ast = pipeline(func_ast, env)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\pipeline.py", line 191, in __call__
    ast = self.transform(ast, env)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\pipeline.py", line 656, in transform
    ast = stage(ast, env)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\pipeline.py", line 641, in _stage
    return _check_stage_object(stage_obj)(ast, env)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\pipeline.py", line 194, in __call__
    ast = self.transform(ast, env)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\pipeline.py", line 474, in transform
    return transformer.visit(ast)
  File "C:\Users\app\Anaconda\lib\ast.py", line 241, in visit
    return visitor(node)
  File "C:\Users\app\Anaconda\lib\ast.py", line 297, in generic_visit
    value = self.visit(value)
  File "C:\Users\app\Anaconda\lib\ast.py", line 241, in visit
    return visitor(node)
  File "C:\Users\app\Anaconda\lib\ast.py", line 297, in generic_visit
    value = self.visit(value)
  File "C:\Users\app\Anaconda\lib\ast.py", line 241, in visit
    return visitor(node)
  File "C:\Users\app\Anaconda\lib\ast.py", line 297, in generic_visit
    value = self.visit(value)
  File "C:\Users\app\Anaconda\lib\ast.py", line 241, in visit
    return visitor(node)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\visitors.py", line 311, in visit_ControlBlock
    self.visitlist(node.body)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\visitors.py", line 286, in visitlist
    list[:] = _flatmap(self.visit, list)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\visitors.py", line 33, in _flatmap
    res = func(elem)
  File "C:\Users\app\Anaconda\lib\ast.py", line 241, in visit
    return visitor(node)
  File "C:\Users\app\Anaconda\lib\ast.py", line 306, in generic_visit
    new_node = self.visit(old_value)
  File "C:\Users\app\Anaconda\lib\ast.py", line 241, in visit
    return visitor(node)
  File "C:\Users\app\Anaconda\lib\ast.py", line 297, in generic_visit
    value = self.visit(value)
  File "C:\Users\app\Anaconda\lib\ast.py", line 241, in visit
    return visitor(node)
  File "C:\Users\app\Anaconda\lib\ast.py", line 297, in generic_visit
    value = self.visit(value)
  File "C:\Users\app\Anaconda\lib\ast.py", line 241, in visit
    return visitor(node)
  File "C:\Users\app\Anaconda\lib\ast.py", line 297, in generic_visit
    value = self.visit(value)
  File "C:\Users\app\Anaconda\lib\ast.py", line 241, in visit
    return visitor(node)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\visitors.py", line 311, in visit_ControlBlock
    self.visitlist(node.body)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\visitors.py", line 286, in visitlist
    list[:] = _flatmap(self.visit, list)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\visitors.py", line 33, in _flatmap
    res = func(elem)
  File "C:\Users\app\Anaconda\lib\ast.py", line 241, in visit
    return visitor(node)
  File "C:\Users\app\Anaconda\lib\ast.py", line 306, in generic_visit
    new_node = self.visit(old_value)
  File "C:\Users\app\Anaconda\lib\ast.py", line 241, in visit
    return visitor(node)
  File "C:\Users\app\Anaconda\lib\ast.py", line 297, in generic_visit
    value = self.visit(value)
  File "C:\Users\app\Anaconda\lib\ast.py", line 241, in visit
    return visitor(node)
  File "C:\Users\app\Anaconda\lib\ast.py", line 297, in generic_visit
    value = self.visit(value)
  File "C:\Users\app\Anaconda\lib\ast.py", line 241, in visit
    return visitor(node)
  File "C:\Users\app\Anaconda\lib\ast.py", line 297, in generic_visit
    value = self.visit(value)
  File "C:\Users\app\Anaconda\lib\ast.py", line 241, in visit
    return visitor(node)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\visitors.py", line 311, in visit_ControlBlock
    self.visitlist(node.body)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\visitors.py", line 286, in visitlist
    list[:] = _flatmap(self.visit, list)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\visitors.py", line 33, in _flatmap
    res = func(elem)
  File "C:\Users\app\Anaconda\lib\ast.py", line 241, in visit
    return visitor(node)
  File "C:\Users\app\Anaconda\lib\ast.py", line 306, in generic_visit
    new_node = self.visit(old_value)
  File "C:\Users\app\Anaconda\lib\ast.py", line 241, in visit
    return visitor(node)
  File "C:\Users\app\Anaconda\lib\ast.py", line 297, in generic_visit
    value = self.visit(value)
  File "C:\Users\app\Anaconda\lib\ast.py", line 241, in visit
    return visitor(node)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\array_expressions.py", line 100, in visit_Assign
    node.value = self.visit(node.value)
  File "C:\Users\app\Anaconda\lib\ast.py", line 241, in visit
    return visitor(node)
  File "C:\Users\app\Anaconda\lib\ast.py", line 306, in generic_visit
    new_node = self.visit(old_value)
  File "C:\Users\app\Anaconda\lib\ast.py", line 241, in visit
    return visitor(node)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\array_expressions.py", line 136, in visit_BinOp
    return self.visit_elementwise(elementwise, node)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\array_expressions.py", line 84, in visit_elementwise
    return self.register_array_expression(node)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\array_expressions.py", line 272, in register_array_expression
    wrap=False, link=False, nopython=True,
  File "C:\Users\app\Anaconda\lib\site-packages\numba\pipeline.py", line 90, in run_pipeline2
    post_ast = pipeline(func_ast, env)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\pipeline.py", line 191, in __call__
    ast = self.transform(ast, env)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\pipeline.py", line 656, in transform
    ast = stage(ast, env)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\pipeline.py", line 641, in _stage
    return _check_stage_object(stage_obj)(ast, env)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\pipeline.py", line 202, in __call__
    reporting.report(env, exc=e)
  File "C:\Users\app\Anaconda\lib\site-packages\numba\reporting.py", line 181, in report
    raise exc
numba.error.NumbaError: (see below)
--------------------- Numba Encountered Errors or Warnings ---------------------
Error 133:22: Cannot coerce to or from object in nopython context
--------------------------------------------------------------------------------

What does this mean? I hope it doesn't mean I can't use objects!

Edit

I've edited all relevant code so that I'm no longer passing any objects around, and the definition now looks like this:

@jit(float_[:,:,:](float_[:,:], int_[:], int_))
def train_function(X, y, H):

But I'm still getting that error, except now it's not Error:133:22, but:

Error 176:22: Cannot coerce to or from object in nopython context

Answer 1

I found out somewhere that Numba doesn't recognize np.dot() directly, and the Error: 176:22 was pointing to line 176, where I was using np.dot(). This was the relevant line:

 dot = 1. + np.dot(X1, g1) - np.dot(X1,gc)

So I cast the dot products it into floats, and it worked:

dot = 1. + float(np.dot(X1, g1)) - float(np.dot(X1,gc))