pocketflow/docs/parallel.md

55 lines
1.9 KiB
Markdown

---
layout: default
title: "(Advanced) Parallel"
parent: "Core Abstraction"
nav_order: 6
---
# (Advanced) Parallel
**Parallel** Nodes and Flows let you run multiple **Async** Nodes and Flows **concurrently**—for example, summarizing multiple texts at once. This can improve performance by overlapping I/O and compute.
## AsyncParallelBatchNode
Like **AsyncBatchNode**, but run `exec_async()` in **parallel**:
```python
class ParallelSummaries(AsyncParallelBatchNode):
async def prep_async(self, shared):
# e.g., multiple texts
return shared["texts"]
async def exec_async(self, text):
prompt = f"Summarize: {text}"
return await call_llm_async(prompt)
async def post_async(self, shared, prep_res, exec_res_list):
shared["summary"] = "\n\n".join(exec_res_list)
return "default"
node = ParallelSummaries()
flow = AsyncFlow(start=node)
```
## AsyncParallelBatchFlow
Parallel version of **BatchFlow**. Each iteration of the sub-flow runs **concurrently** using different parameters:
```python
class SummarizeMultipleFiles(AsyncParallelBatchFlow):
async def prep_async(self, shared):
return [{"filename": f} for f in shared["files"]]
sub_flow = AsyncFlow(start=LoadAndSummarizeFile())
parallel_flow = SummarizeMultipleFiles(start=sub_flow)
await parallel_flow.run_async(shared)
```
## Best Practices
- **Ensure Tasks Are Independent**: If each item depends on the output of a previous item, **do not** parallelize.
- **Beware of Rate Limits**: Parallel calls can **quickly** trigger rate limits on LLM services. You may need a **throttling** mechanism (e.g., semaphores or sleep intervals).
- **Consider Single-Node Batch APIs**: Some LLMs offer a **batch inference** API where you can send multiple prompts in a single call. This is more complex to implement but can be more efficient than launching many parallel requests and mitigates rate limits.