Disclaimer: ChatGPT generated document.
In computing, batch and coalesce refer to two different concepts used to optimize performance, though they’re often related in scenarios involving data processing, memory operations, or network requests.
Batching means grouping multiple operations or items together and executing them as a single unit rather than individually.
- Reduces overhead (e.g., fewer function calls, fewer I/O or network roundtrips).
- Improves efficiency and throughput.
- Often processed non-interactively or scheduled.
| Context | Example |
|---|---|
| Database | Insert 100 rows in one query instead of 100 separate queries. |
| GPU processing | Submit a set of draw calls at once. |
| Operating systems | "Batch jobs" that run overnight. |
| Networking | Send data in larger packets rather than multiple small ones. |
| File processing | Batch renaming files. |
To coalesce means to combine adjacent or related elements to avoid fragmentation or inefficiency. It focuses more on merging than grouping operations.
- Reduces fragmentation.
- Lowers the number of operations by merging small ones.
- Often used in memory/numerical contexts.
| Context | Example |
|---|---|
| Memory allocation | Merge adjacent free memory blocks into one large block. |
| Databases | COALESCE(expr1, expr2) → returns the first non-null value. |
| Network data | Combine multiple small writes into a single packet. |
| File systems | Coalesce small logs into one contiguous write. |
| Multi-threading | Coalescing thread wake-ups to reduce context switches. |
| GPU memory access | Coalesced memory access reduces number of transactions. |
| Aspect | Batch | Coalesce |
|---|---|---|
| Focus | Group tasks | Merge adjacent items |
| Typical use | Operations & processing | Memory/data layout |
| Goal | Efficient execution | Reduced fragmentation |
| Example | Insert N items at once | Merge adjacent free blocks |
They often work together. For example, if you batch multiple network writes, the system might coalesce them into one efficient transfer.
Batch: "Instead of sending 10 letters separately, put them all in one envelope."
Coalesce: "Instead of using 3 envelopes glued together, use one big envelope."
- Batch = perform multiple actions together.
- Coalesce = merge items to eliminate fragmentation or inefficiency.
Used properly, both are powerful techniques for optimizing performance in systems, parallel programming, database operations, compilers, and more.
If you'd like, I can expand with examples in:
👉 C++ memory allocators, GPU programming (memory coalescing is especially interesting), or network I/O handling (send() coalescing in TCP). Just let me know!