Code Translation: OpenMP to Python

Parallel For to Pool.map

// OpenMP
#pragma omp parallel for reduction(+:total)
for (int i = 0; i < n; i++) { total += arr[i]; }

# Python
from multiprocessing import Pool
import numpy as np

chunks = np.array_split(arr, n_workers)
with Pool(n_workers) as pool:
    total = sum(pool.map(np.sum, chunks))

Sections to Processes

// OpenMP
#pragma omp parallel sections
{ #pragma omp section
  task_a(); #pragma omp section
  task_b(); }

# Python
from multiprocessing import Process
p1, p2 = Process(target=task_a), Process(target=task_b)
p1.start(); p2.start(); p1.join(); p2.join()

Critical Section to Lock

// OpenMP: #pragma omp critical { counter++; }

# Python
from multiprocessing import Lock, Value
counter = Value('i', 0); lock = Lock()
with lock: counter.value += 1

Barrier

// OpenMP: #pragma omp barrier

# Python
from multiprocessing import Barrier
barrier = Barrier(n_workers); barrier.wait()

Private Variables

// OpenMP: #pragma omp parallel for private(temp)

# Python - automatic in processes
def worker(i):
    temp = compute(i)  # Private by default
    return temp * 2

with Pool(4) as pool:
    result = pool.map(worker, range(n))

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