Virtu Financial Inc. postponed its IPO last year and are slated to start trading on Thursday in a possible sign that angst over “high frequency” trading is slowing down. Virtu, whose shares will trade under the symble “VIRT” on the Nasdaq, is offering 16.5 million class A shares that are expected to be priced at $17-$19 a share, valuing the company at $2.6 billion. Virtu hopes to raise as much as $314 million. Doug Cifu, chief executive of Virtu said, “I thought it was a good thing to disclose to the world that the firm was profitable everyday like McDonald’s and a lot of other firms are. But, boy, did that backfire in my face.” He told Sandler O’Neil conference last year.