Numba and PySpark users?

Is anyone using Numba with PySpark?

I’m just starting to experiment with this - it seems that Numba can be used in PySpark pandas UDFs, for example, as long as the series is adapted to an ndarray: numba-pyspark-udfs/ at main · gmarkall/numba-pyspark-udfs · GitHub - however, I noticed that PySpark called the Numba function multiple times elementwise, in my naive first implementation.

We use numba extensively for simulations using pyspark, though quite differently than the way you’re doing it with pandas and udfs.

If you’re interested in a mapPartitions-style example with numba, let me know and I’ll make a little demo.

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Thanks for the reply - if you’re able to and it’s not too much trouble, a small demo of the way you’re using it would be great to see - many thanks in advance :slight_smile:

Here’s a mini-demo, let me know if you have questions

from numba import njit
import numpy
from functools import partial

df = spark.sparkContext.parallelize([(i, i * i) for i in range(10)]).toDF(['i', 'i_squared']).cache()
print('original dataframe')

# convert the dataframe to a dict[string, ndarray]
# this is inefficient, just an example
def columns_to_ndarray(partition_number, iter):
    # this function runs in plain-python space on the executor
    res = {}
    for row in iter:
        row = row.asDict()
        if not res:
            res = {key: [] for key, val in row.items()}
        [res[key].append(val) for key, val in row.items()]
    yield {key: numpy.asarray(lst) for key, lst in res.items()}

ndarray_rdd = df.rdd.mapPartitionsWithIndex(columns_to_ndarray).cache()
print('converted to dict[column name, ndarray]')
for partition, data in enumerate(ndarray_rdd.collect()):
    print('partition=', partition, 'data=', data)

def numba_invert(input_array):
    result = numpy.empty_like(input_array)
    for i in range(len(input_array)):
        result[i] = input_array[i] * -1
    return result

def invert_column(column_name, partition_number, iter):
    for item in iter:  # loop over the dictionaries, one per partition
        item[column_name] = numba_invert(item[column_name])
        yield item    

i_plus_one_rdd = ndarray_rdd.mapPartitionsWithIndex(partial(invert_column, 'i')).cache()
print('numpy inverted column i')
for partition, data in enumerate(i_plus_one_rdd.collect()):
    print('partition=', partition, 'data=', data)