I used NR a bit more in grad school (late 80s/early 90s) than undergrad. I had (have) the Fortran version. I used some of the ODE integration bits in some code I worked on in grad school, though we put that project away after we switched to a different DFT MD code. FWIW, that code (with NR) still compiles/runs. Tried it a few months ago.<p>As an undergrad, I had a research project which used Markov methods, and I had to generate some fairly large (at the time) matrices. I wrote that code in Fortran, on a PC/AT system (1986, so ...). It also ran on an IBM 3090 VF 180 mainframe at Stony Brook.<p>What I recall from that time, was the professor giving me a text on Markov methods, and me learning what I needed to construct the transition probabilities (matrix elements). I remember writing extensive tests within the code, called sanity checks, which I reported on. Fortran, no assert statement at the time, and its nice to see a note "COMPUTATION IS INSANE DO NOT TRUST" error message when you ran into problems.<p>Honestly, that process taught me a number of things.<p>1st, the code you need may or may not have been written by someone else, and you really need to make sure you have sanity checks built in to establish the portions you can and cannot trust. Later when I used the NR code, I added sanity checks into their code, to make sure we weren't getting into strange spaces.<p>2nd, it is (often very) important to exploit mathematical features of your problems (symmetries, relation of derivatives to exact closed form equations, etc.) to simplify your calculation. Plug and crank is usually the wrong approach, and you need a solid understanding of your problem domain to have a fighting chance at not producing a garbage simulation.<p>I've followed these coding practices for decades at this point, through many languages and systems. NR was a great way to start with these things, but I picked up Hamming's, Hildebrant's, and many other numerical analysis books along the way, taught myself, and generated code that was hopefully sane.<p>I don't care so much about the license of NR, as I am not distributing code containing it. My thesis advisor warned me about that in early 90s. So that was removed from code I shared.<p>I guess I am a bit sad that I offered said book to offspring as she starts a PhD in MechE later this year, and I don't think she wants it. She did take my numerical analysis books though, so I'm happy about that.