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Add notes on templight for compile time perf

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Jason Turner
2015-06-08 10:15:37 -06:00
parent 2de6bbce8c
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07-Considering_Performance.md
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@@ -39,17 +39,24 @@ Templates are not free to instantiate. Instantiating many templates, or template
For more examples see [this article](http://blog2.emptycrate.com/content/template-code-bloat-revisited-smaller-makeshared). For more examples see [this article](http://blog2.emptycrate.com/content/template-code-bloat-revisited-smaller-makeshared).
## Firewall Frequently Changing Header Files
### Analyze the Build
The tool [Templight](https://github.com/mikael-s-persson/templight) can be used to analyze the build time of your project. It takes some effort to get built, but once you do, it's a drop in replacement for clang++.
After you build using Templight, you will need to analyze the results. The [templight-tools](https://github.com/mikael-s-persson/templight-tools) project provides various methods. (Author's Note: I suggest using the callgrind converter and visualizing the results with kcachegrind).
### Firewall Frequently Changing Header Files
### Don't Unnecessarily Include Headers #### Don't Unnecessarily Include Headers
The compiler has to do something with each include directive it sees. Even if it stops as soon as it seems the `#ifndef` include guard, it still had to open the file and begin processing it. The compiler has to do something with each include directive it sees. Even if it stops as soon as it seems the `#ifndef` include guard, it still had to open the file and begin processing it.
[include-what-you-use](https://code.google.com/p/include-what-you-use) is a tool that can help you identify which headers you need. [include-what-you-use](https://code.google.com/p/include-what-you-use) is a tool that can help you identify which headers you need.
### Reduce the load on the preprocessor #### Reduce the load on the preprocessor
This is a general form of "Firewall Frequently Changing Header Files" and "Don't Unnecessarily Include Headers." Tools like BOOST_PP can be very helpful, but they also put a huge burden on the preprocessor. This is a general form of "Firewall Frequently Changing Header Files" and "Don't Unnecessarily Include Headers." Tools like BOOST_PP can be very helpful, but they also put a huge burden on the preprocessor.