python - Numba 比普通 python 慢得多，来自 Pandas 文档

Question

我的目标是复制 pandas 文档增强执行指南的结果。 https://pandas.pydata.org/pandas-docs/stable/user_guide/enhancingperf.html

示例的 numba 实现应该非常快，甚至比 Cython 实现还要快。我成功地实现了 Cython 代码，但是虽然 Numba 应该很容易实现（只是添加一个装饰器对吗？）它超级慢，甚至比普通的 python 实现还要慢。有谁知道怎么回事？

结果：

代码：

import pandas as pd
import numpy as np
import time
import numba

import cpythonfunctions



def f(x):
    return x * (x - 1)


def integrate_f(a, b, N):
    s = 0
    dx = (b - a) / N
    for i in range(N):
        s += f(a + i * dx)
    return s * dx

@numba.jit
def f_plain_numba(x):
    return x * (x - 1)


@numba.jit(nopython=True)
def integrate_f_numba(a, b, N):
    s = 0
    dx = (b - a) / N
    for i in range(N):
        s += f_plain_numba(a + i * dx)
    return s * dx


@numba.jit(nopython=True)
def apply_integrate_f_numba(col_a, col_b, col_N):
    n = len(col_N)
    result = np.empty(n, dtype="float64")
    assert len(col_a) == len(col_b) == n
    for i in range(n):
        result[i] = integrate_f_numba(col_a[i], col_b[i], col_N[i])
    return result

if __name__ == "__main__":
    df = pd.DataFrame(
        {
            "a": np.random.randn(1000),
            "b": np.random.randn(1000),
            "N": np.random.randint(100, 1000, (1000)),
            "x": "x",
        }
    )


    start = time.perf_counter()
    df.apply(lambda x: integrate_f(x["a"], x["b"], x["N"]), axis=1)
    print('pure python takes {}'.format(time.perf_counter() - start))

    '''
    CYTHON
    '''
    # cythonize the functions (plain python functions to C)
    start = time.perf_counter()
    df.apply(lambda x: cpythonfunctions.integrate_f_plain(x["a"], x["b"], x["N"]), axis=1)
    print('cython takes {}'.format(time.perf_counter() - start))

    # create cdef and cpdef (typed fucntions, with int, double etc..)
    start = time.perf_counter()
    df.apply(lambda x: cpythonfunctions.integrate_f_typed(x["a"], x["b"], x["N"]), axis=1)
    print('cython typed takes {}'.format(time.perf_counter() - start))

    # In above function, most time was spend calling series.__getitem__ and series.__get_value
    # ---> This stems from the apply apart. Cythonize this!
    start = time.perf_counter()
    cpythonfunctions.apply_integrate_f(df["a"].to_numpy(), df["b"].to_numpy(), df["N"].to_numpy())
    print('cython integrated takes {}'.format(time.perf_counter() - start))


    # Remove memory checks
    start = time.perf_counter()
    cpythonfunctions.apply_integrate_f_wrap(df["a"].to_numpy(), df["b"].to_numpy(), df["N"].to_numpy())
    print('cython integrated takes {}'.format(time.perf_counter() - start))

    '''
    including JIT
    '''

    start = time.perf_counter()
    apply_integrate_f_numba(df["a"].to_numpy(), df["b"].to_numpy(), df["N"].to_numpy())
    print('numba.jit apply integrate takes {}'.format(time.perf_counter() - start))

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