The Singleton
This EA implements the Singleton design pattern for MQL5 Expert Advisors, ensuring only one instance of the EA can run on a terminal at a time. It prevents duplicate instances from executing simultaneously, which could cause conflicting trades or resource conflicts. The core functionality is a protective utility mechanism rather than a trading strategy.
Open the interactive view (equity curve, symbol switch)Key facts
Backtest results (H1, about 1 year)
Not backtested yet — this EA could not be converted automatically.
Strategy analysis
This EA implements the Singleton design pattern rather than a trading strategy, ensuring only one EA instance runs per terminal. Entry conditions are not applicable since the EA does not execute any trades. Exit conditions are similarly not applicable; the EA only monitors and blocks duplicate instances. Position sizing is not involved as there is no trade-opening behavior. Money management is irrelevant since the EA does not handle any capital-related logic. The mechanism typically uses global variables, file-based locks, or chart scanning to detect and prevent duplicate instances from running simultaneously, protecting against conflicting orders or resource contention.
Strengths
- Prevents trade conflicts caused by multiple EA instances running simultaneously
- Provides architectural-level protection reducing risk of human operational errors
- Simple and effective implementation without adding complexity to trading logic
Weaknesses
- Does not execute any trading strategy, serving only as an auxiliary utility
- May prevent legitimate multi-symbol deployment of the same strategy
- Lacks detailed configuration options, limiting flexibility
Possible improvements
- Add a whitelist feature allowing multiple instances on specific symbols or charts
- Add logging functionality to record instance creation and blocking events
Risk assessment
Overall risk: Safe
- Failure of the blocking mechanism could lead to multi-instance conflicts
- Lack of persistent logging for blocked instance events
Evaluation scores
Parameters
| Parameter | Default | Description |
|---|---|---|
Singleton Enabled | true | Enable singleton mode protection |
Alert on Duplicate | true | Alert when duplicate instance detected |
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Backtests are historical simulations and do not guarantee future results. Not financial advice.