Making sure that some piece of software doesn't run afoul of an existing patent is basically impossible no matter how many billable lawyer hours you throw at the problem. You'll either come to the conclusion that everything has already been patented and thus you can never build anything ever again, if you read patents broadly, or you won't find anything at all, if you read them more narrowly and throw out the ones that obviously have prior art and should never have been granted.

The only 100% reliable method of patent lawsuit control is software development abstinence . . .