In the sorts of searches I often do, like fitting integer solutions to fast function approximations, searching for error correcting codes, and randomized SAT-li

In the sorts of searches I often do, like fitting integer solutions to fast function approximations, searching for error correcting codes, and randomized SAT-like problems, or simulating usage of data structures for benchmarking them chacha is slow enough to meaningfully influence (even dominate) the runtime. I wouldn't want to use rand() because it's extremely likely that it will produce actually bad results. I agree one should use a CSPRNG like chacha (or rdrand) if its runtime is insignificant but then the question is: whats the best choice when it's not insignificant? Using rand is a bad idea.