I've seen a Mersenne twister in the wild, implemented in Excel VBA. The small differences in numeric behaviour caused the author to re-implement basic numeric operations like additions.<p>It was used in a Mone Carlo simulation implemented on data in excel sheet. The thing was 4K lines of VBA and was extermely slow: It did its simulation over 8 hours for a few 100K iterations.<p>Someone had given it to a 'High performance excel developer' company (!) and they ran into their limits. I reimplemented it in single threaded C in the evening, and it did its thing in seconds. But that was not acceptable, as the end user could not adapt the VBA anymore.<p>So I dumped only the Mersenne twister in a DLL, imported that in VBA, and it gained 10% speed, basically all time spent in the RNG. I suggested moving other parts to C, but they didn't want to break ties with the excel programmers and nothing came from it.