This page explains some common troubleshooting topics that arise for backtests.

Speed Issues

If you notice that backtests run faster in QuantConnect Cloud than on-premise, it's likely because we host special hardware that's optimized for LEAN. For more information about our hardware, see Backtesting Nodes.

Local and Cloud Result Differences

If your algorithm produces different results when you backtest it in QuantConnect Cloud versus on-premise, it's usually because of differences in data. For example, if you don't have the latest version of the US Equity Security Master, you will likely be missing some splits and dividends, which impact the historical prices of adjusted data. In this case, to avoid differences in the backtest results, update your local copy of the US Equity Security Master every day. For more information about downloading data from the Dataset Market so you have the same data on-premise as in QuantConnect Cloud, see Downloading Data.

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