I once held the record for the most “CTUs” used by a successfully terminating program.
In grad school, I was the only computer scientist in the chaos class. Though some of the math was over my head, the mathemeticians were delighted to have a computer scientist who could get their graphs done in a reasonable time without being yelled at by the VAX manager. They were trying to draw “Julia Sets” by “basins of attraction,” and the only picture they’d managed to get was 16 by 16 pixels and that took days of computer time.
I used the “Cyber” computer (that everybody looked down on) because it was really fast and I could schedule a job for 2:30 am when it wasn’t doing anything else. The next day, my CTU balance was negative bazillions and I had to ask the “MUCKM00” to let me log in. There was the output file, but the program hadn’t finished running till like 3 in the afternoon! I then passed the file through my Z80 computer to my IDS “Prism” printer and got a full page drawing of the julia set.
Once the mathemeticians saw that it was all yellow and black, they looked at their equations and found the mistake. They were expecting multi-color basins and the set itself in black. The corrected program produced the multi-color drawing a couple nights later in about 10 minutes.
The cyber staff teased me the whole school year over that[:D]