PC-1211, PC-1250, etc. TVM

[robve]

(06-11-2024 10:32 PM)dm319 Wrote:  

(06-11-2024 07:13 PM)robve Wrote:  An improved version of the TVM program for SHARPs.

Great work!! Very impressive to fit all this in these lines of code. Also a very interesting performance profile. Eyeballing it, very close to the HP-37, sometimes identical. I will put it into the results table and I'm curious to run the dimension reduction on it again and see where it pops up. I'd be curious of a video of it in action solving tvm problems if you ever find the time.

Thanks. I still want to give the Albert's suggested modified Newton's method a try to compare efficiency of TVM rate calculations, but haven't had the time yet. Working in non-IEEE754 is a pain. Some things just don't work out numerically as we're stuck with 10 digits to store in variables (internal calculations are 12 digits). Results and behaviors of the C implementation don't necessarily translate, as can be expected, hence the challenge. The current method finds the root with a few NPMT evaluations. I was surprised that some roots are found in just 3 evaluations as you can see in the results.

Now, I'm curious how the SHARP PC-1421 fares on these TVM problems. I don't have access to one at the moment, but could try an emulator. It's a machine that supports TVM operations on the keypad but also directly within BASIC, i.e. setting TVM variable PV=x is just an assignment. Computing is done with e.g. COMP PMT that updates the PMT variable. It also has cash flow and IRR calculations. This should be very handy to write specialized financial applications (which is not my thing). It seems that the PC-1421 was not popular, perhaps because financial people don't write BASIC? Wrong target audience? The machine is a bit weird and that's why it intrigues me.

- Rob