Menene bambanci tsakanin concurrency da parallelism?

Question

IT Interview Practice · Accepted Answer

**Concurrency yana da alaƙa da *sarrafa* abubuwa da yawa a lokaci guda; parallelism yana da alaƙa da *yin* abubuwa da yawa a lokaci guda.** Concurrency hanya ce ta tsara shirin domin ayyuka da yawa su ci gaba ta hanyar interleaving; parallelism a zahiri yana aiwatar da su a lokaci guda a kan cores da yawa.

## Yadda yake aiki

CPU core ɗaya na iya zama **concurrent** amma ba parallel ba: yana canzawa da sauri tsakanin ayyuka, don haka suna cuɗanya cikin lokaci ko da yake ɗaya kawai ke gudana a kowane lokaci. **Parallelism** yana buƙatar cores da yawa da ke gudanar da umarni a lokaci guda.

```text
Concurrency (1 core, interleaved):   A--B--A--B--A--B
Parallelism (2 cores, simultaneous): A--A--A--A
                                     B--B--B--B
```

## Misali

```python
# Concurrency: one thread juggles two downloads by waiting on I/O
async def main():
    await asyncio.gather(fetch(url1), fetch(url2))  # overlap, one core

# Parallelism: two CPU cores crunch numbers at the same time
with ProcessPoolExecutor() as pool:
    pool.map(heavy_compute, data)  # truly simultaneous
```

Taƙaitawar Rob Pike: "Concurrency yana da alaƙa da tsari, parallelism yana da alaƙa da aiwatarwa." Kana iya samun concurrency ba tare da parallelism ba (async I/O a kan core ɗaya) kuma sau da yawa suna haɗuwa.

## Me ya sa yake da muhimmanci

Masu tambaya suna amfani da wannan don duba ko ka fahimci *dalilin* da threads ke taimakawa. Aikin I/O-bound yana amfana daga concurrency (cuɗanya jira); aikin CPU-bound yana buƙatar parallelism (ƙarin cores). Rikita su yana kaiwa ga ƙira da ke ƙara threads amma ba ta ganin haɓaka.

Yadda yake aiki

Misali

Me ya sa yake da muhimmanci

Tambayoyi masu alaƙa