What good does it do to pray about anything if the outcome is not affected? I would say when God chooses which world to actualize, he takes into account the prayers that would be offered in that world. We shouldn't think prayer is about changing the mind of God. He's omniscient; he already knows the future, but prayer makes a difference in that it can affect what world God has chosen to create.

Kate Shellnutt (31 January 2014), "William Lane Craig: God Hears Your Super Bowl Prayers", Christianity Today, ISSN 0009-5753