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[no-ci] Update basics.md

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Daniel Lemire
2024-07-31 11:10:01 -04:00
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@@ -2652,7 +2652,8 @@ Performance tips
- Read [our performance notes](performance.md) for advanced topics.
- The On-Demand front-end works best when doing a single pass over the input: avoid calling `count_elements`, `rewind` and similar methods.
- To better understand the operation of your On-Demand parser, and whether it is performing as well as you think it should be, there is a logger feature built in to simdjson! To use it, define the pre-processor directive `SIMDJSON_VERBOSE_LOGGING` prior to including the `simdjson.h` header, which enables logging in simdjson. Run your code. It may generate a lot of logging output; adding printouts from your application that show each section may be helpful. The log's output will show step-by-step information on state, buffer pointer position, depth, and key retrieval status. Importantly, unless `SIMDJSON_VERBOSE_LOGGING` is defined, logging is entirely disabled and thus carries no overhead.
- The On-Demand front-end works best when doing a single pass over the input: avoid calling `count_elements`, `rewind`, `reset` and similar methods.
- If you are familiar with assembly language, you may use the online tool godbolt to explore the compiled code. The following example may work: [https://godbolt.org/z/xE4GWs573](https://godbolt.org/z/xE4GWs573).
- Given a field `field` in an object, calling `field.key()` is often faster than `field.unescaped_key()` so if you do not need an unescaped `std::string_view` instance, prefer `field.key()`. Similarly, we expect `field.escaped_key()` to be faster than `field.unescaped_key()` even though both return a `std::string_view` instance.
- For release builds, we recommend setting `NDEBUG` pre-processor directive when compiling the `simdjson` library. Importantly, using the optimization flags `-O2` or `-O3` under GCC and LLVM clang does not set the `NDEBUG` directive, you must set it manually (e.g., `-DNDEBUG`).
@@ -2672,7 +2673,6 @@ Performance tips
std::string_view year = data["year"];
std::string_view rating = data["rating"];
```
- To better understand the operation of your On-Demand parser, and whether it is performing as well as you think it should be, there is a logger feature built in to simdjson! To use it, define the pre-processor directive `SIMDJSON_VERBOSE_LOGGING` prior to including the `simdjson.h` header, which enables logging in simdjson. Run your code. It may generate a lot of logging output; adding printouts from your application that show each section may be helpful. The log's output will show step-by-step information on state, buffer pointer position, depth, and key retrieval status. Importantly, unless `SIMDJSON_VERBOSE_LOGGING` is defined, logging is entirely disabled and thus carries no overhead.