When Livermore contracted to buy its first vector machine (Star-100 from CDC?) it began preparing by writing a set of macros to emulate vector logic on the CDC 6600.
Production 6600 programs were substantially modified to use these macros for the bulk of their work.
This was to debug vector logic, not for production.
To the embarrassment of some but the ultimate delight of most the new program ran faster.
The 6600 was very good at loops that fit in 120 bits.
The vector versions supplanted the earlier point by point versions and the transition was eased.