Took a look and while I don't find DM's coding style particularly readable I did find this:
/* Spend X% of SP get X/2% of lost HP. E.g., at 50% HP get X/4% */
/* Gain stays low at msp<10 because MP gains are generous at msp<10 */
/* sp_ratio is max sp to spent sp, doubled to suit target rate. */
|