https://www.mql5.com/en/book

- www.mql5.com
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EAs : Don't do per tick what you can do per bar, or on open.
If you are waiting for a level, don't reevaluate, wait until price reaches it (or a new bar starts, and you recalculate.)
If you are waiting for an order to close, only look when OrdersTotal has changed. (In MT5 capture the deal out)
How to get backtesting faster ? - MT4 - MQL4 programming forum (2017) -
Indicators: Code it properly so it only recomputes bar zero (after the initial run).
How to do your lookbacks correctly. (2016)
3 Methods of Indicators Acceleration by the Example of the Linear Regression - MQL5 Articles. (2011)
Or, reduce Tools → Options (control+O) → Charts → Max bars in chart to something reasonable (like 1K.)
Please consider which section is most appropriate — https://www.mql5.com/en/forum/172166/page6#comment_49114893
I've been wondering what tips do you follow so that your Expert Advisors use are more stable, use less pc resources, not freeze, etc.