For my backtesting, I find it is the most difficult to obtain reliable and clean historical data with detailed information such as bid and ask spreads. What is the best software for strategy backtesting? And I am looking for those software that allow for testing "creative" trade ideas... for example, if I want to explore correlation among different global markets and different asset classes, I hope the software can make it easy for me... Are there any good back-testing software that offer free trial so that interested investors can take a trial? Thanks