# Using builtin round() in numba

**URL:** <https://numba.discourse.group/t/using-builtin-round-in-numba/753>\
**Category:** Support: How do I do ...?\
**Created:** [June 14, 2021, 12:47pm UTC](https://numba.discourse.group/t/using-builtin-round-in-numba/753 "2021-06-14T12:47:23Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![caniko](https://yyz2.discourse-cdn.com/free1/user_avatar/numba.discourse.group/caniko/32/334_2.png) [@caniko](https://numba.discourse.group/u/caniko)\
**Post date:** [June 14, 2021, 12:47pm UTC](https://numba.discourse.group/t/using-builtin-round-in-numba/753/1 "2021-06-14T12:47:23Z")

</div>

I am trying to use `round()` in my function (`fps` is 14 as integer):

```python
@jit(nopython=True)
def freezing_time(
    fps: Union[float, int],
    *displacements: Iterable[np.ndarray],
    second_threshold: float = 1.0,
    metric_displacement_threshold: float = 0.005,
):
    frame_threshold = round(second_threshold * fps)

```

Numba is complaining about the round function not being supported in the way I am using. Not sure what is wrong here, any help is appreciated.

Here is the error log:

```auto
Traceback (most recent call last):
  File "/home/can/PycharmProjects/BiKiPy/examples/nort_belhaj_analysis/nort_analysis.py", line 92, in <module>
    NortExperiment(
  File "/home/can/PycharmProjects/BiKiPy/bikipy/behaviour/nort/experiment.py", line 139, in __init__
    exp := NortHabituationTrial(
  File "/home/can/PycharmProjects/BiKiPy/bikipy/behaviour/nort/trial.py", line 145, in __init__
    self.freezing_time
  File "/home/can/.pyenv/versions/3.9.4/lib/python3.9/functools.py", line 969, in __get__
    val = self.func(instance)
  File "/home/can/PycharmProjects/BiKiPy/bikipy/behaviour/nort/trial.py", line 149, in freezing_time
    return freezing_time(
  File "/home/can/.cache/pypoetry/virtualenvs/bikipy-V2iGsb6g-py3.9/lib/python3.9/site-packages/numba/core/dispatcher.py", line 420, in _compile_for_args
    error_rewrite(e, 'typing')
  File "/home/can/.cache/pypoetry/virtualenvs/bikipy-V2iGsb6g-py3.9/lib/python3.9/site-packages/numba/core/dispatcher.py", line 361, in error_rewrite
    raise e.with_traceback(None)
numba.core.errors.TypingError: Failed in nopython mode pipeline (step: nopython frontend)
No implementation of function Function(<built-in function round>) found for signature:
 
 >>> round(array(float64, 1d, C))
 
There are 2 candidate implementations:
   - Of which 2 did not match due to:
   Type Restricted Function in function 'round': File: unknown: Line unknown.
     With argument(s): '(array(float64, 1d, C))':
    No match for registered cases:
     * (float32,) -> int64
     * (float64,) -> int64
     * (float32, int64) -> float32
     * (float64, int64) -> float64

During: resolving callee type: Function(<built-in function round>)
During: typing of call at /home/can/PycharmProjects/BiKiPy/bikipy/feature/motion.py (149)

File "../../bikipy/feature/motion.py", line 149:
def freezing_time(
    <source elided>
    """
    frame_threshold = round(second_threshold * fps)
    ^

```

---

<div class="post-metadata">

**Author:** ![Hannes](https://yyz2.discourse-cdn.com/free1/user_avatar/numba.discourse.group/hannes/32/188_2.png) [@Hannes](https://numba.discourse.group/u/Hannes)\
**Post date:** [June 14, 2021, 3:23pm UTC](https://numba.discourse.group/t/using-builtin-round-in-numba/753/2 "2021-06-14T15:23:45Z")

</div>

Hi @caniko

How are you calling that function? The signature suggests that `second_threshold` and `fps` are scalars. But the error message looks to me as if at least one of them was passed as a numpy array. If that is indeed the case you need to use numpy’s round function, if not something might be fishy.

Does this function run without the jit-decorator?

---

<div class="post-metadata">

**Author:** ![caniko](https://yyz2.discourse-cdn.com/free1/user_avatar/numba.discourse.group/caniko/32/334_2.png) [@caniko](https://numba.discourse.group/u/caniko)\
**Post date:** [June 14, 2021, 5:31pm UTC](https://numba.discourse.group/t/using-builtin-round-in-numba/753/3 "2021-06-14T17:31:57Z")

</div>

```auto
freezing_time(
    self.fps,
    *tuple(np.ndarray, ...),
)

```

I always thought that whatever is inside the tuple fell under `displacements`, but you are that is not the case, or?

---

<div class="post-metadata">

**Author:** ![Hannes](https://yyz2.discourse-cdn.com/free1/user_avatar/numba.discourse.group/hannes/32/188_2.png) [@Hannes](https://numba.discourse.group/u/Hannes)\
**Post date:** [June 16, 2021, 6:19am UTC](https://numba.discourse.group/t/using-builtin-round-in-numba/753/4 "2021-06-16T06:19:12Z")

</div>

mhm, maybe what I wrote was not fully clear: I agree with you that everything in `*tuple(....)` should go into `*displacements`. But that is not the problem here, as far as I can tell.

Are you sure that `self.fps` is a scalar? Or is it something funny like a numpy array with a single entry? `round` is a python builtin and does not work with numpy arrays (even without numba). That is why I asked if your code runs when you remove the numba decorator, or if that also fails (then it is clearly not numba’s fault)

If `self.fps` is a plain python float variable, then there is a problem indeed.

To illustrate my point:

```python
In [1]: import numpy

In [2]: from numba import njit

In [3]: @njit
   ...: def fun(fps):
   ...: return round(fps)
   ...: 

In [4]: fun(14.5) # This runs as expected
Out[4]: 14

In [5]: fun(numpy.array([1.5])) # This throws the same error as in your initial post
---------------------------------------------------------------------------
TypingError Traceback (most recent call last)
<ipython-input-5-ae319fb423de> in <module>
----> 1 fun(numpy.array([1.5]))

~/anaconda3/envs/py38/lib/python3.8/site-packages/numba/core/dispatcher.py in _compile_for_args(self, *args, **kws)
    418 e.patch_message(msg)
    419 
--> 420 error_rewrite(e, 'typing')
    421 except errors.UnsupportedError as e:
    422 # Something unsupported is present in the user code, add help info

~/anaconda3/envs/py38/lib/python3.8/site-packages/numba/core/dispatcher.py in error_rewrite(e, issue_type)
    359 raise e
    360 else:
--> 361 raise e.with_traceback(None)
    362 
    363 argtypes = []

TypingError: Failed in nopython mode pipeline (step: nopython frontend)
No implementation of function Function(<built-in function round>) found for signature:
 
 >>> round(array(float64, 1d, C))
 
There are 2 candidate implementations:
  - Of which 2 did not match due to:
  Type Restricted Function in function 'round': File: unknown: Line unknown.
    With argument(s): '(array(float64, 1d, C))':
   No match for registered cases:
    * (float32,) -> int64
    * (float64,) -> int64
    * (float32, int64) -> float32
    * (float64, int64) -> float64

During: resolving callee type: Function(<built-in function round>)
During: typing of call at <ipython-input-3-66bd25b7c3c2> (3)

File "<ipython-input-3-66bd25b7c3c2>", line 3:
def fun(fps):
    return round(fps)
    ^

```