Another somewhat controversial trading practice closely tied to algorithmic trading is high-frequency trading (HFT). High-frequency trading is the practice, made possible by high-speed computers, of posting and cancelling hundreds or thousands of orders per minute in the hopes of beating competitors’ price quotes and executing trades. HFT may increase the perception of liquidity and lead to increased opportunity costs for investors who do not engage in HFT and who post what they think are competitive bids. Co-location of traders’ computers with marketplace computers can assist in this regard. 7 A related practice is known as flash trading. Flash trading refers to the practice of posting order prices to one ATS a split second before posting them to other marketplaces or permitting some dealers to view orders ahead of other market participants. Opponents argue it creates an informational advantage that allows the market segment privileged by the ATS seeing the order first to execute the trade ahead of other potential counterparties.