Compiling an array of conditions with numba.jit takes a lot of time

Question

If I try to compile a function containing an array of conditions with a numba jit compiler, it will take a very long time. The program looks essentially like

from numba import jit
import numpy as np

@jit(nopython=True)
def foo(a, b):
    valid = [
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0),
        (a - 1 >= 0) and (b - 1 >= 0)
    ]

foo(1, 1)

where I ruled out everything that won't change compile time significantly. The problem arises if I use more than 20 elements.

| elements | time |
-------------------
|    21    | 2.7s |
|    22    | 5.1s |
|    23    |  10s |
|   ...    |  ... |
-------------------

Despite this, the function works well. Does anyone know why it takes so long to compile such a function with numba? Creating arrays in the same way with combinations of integers or floats does not cause problems.

Answer 1

• , numba , , - , .

• , , , . . , valid ?

• , numba .

:

# "codegen"
for i in range(23):
    print(f'    valid[{i}] = (a - 1 >= 0) and (b - 1 >= 0)')

@jit(nopython=True)
def foo(a, b):
    valid = np.empty(23, dtype=np.bool_)
    valid[0] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[1] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[2] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[3] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[4] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[5] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[6] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[7] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[8] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[9] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[10] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[11] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[12] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[13] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[14] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[15] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[16] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[17] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[18] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[19] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[20] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[21] = (a - 1 >= 0) and (b - 1 >= 0)
    valid[22] = (a - 1 >= 0) and (b - 1 >= 0)

%time foo(1,1)
Wall time: 274 ms