Calc saves certain values after
they have been computed once. For example, the P
(calc-pi) command initially “knows” the
constant ‘pi’
to about 20 decimal places; if the current precision is greater
than this, it will recompute ‘pi’ using a series approximation. This
value will not need to be recomputed ever again unless you raise
the precision still further. Many operations such as logarithms
and sines make use of similarly cached values such as
‘pi/4’ and
‘ln(2)’. The
visible effect of caching is that high-precision computations may
seem to do extra work the first time. Other things cached include
powers of two (for the binary arithmetic functions), matrix
inverses and determinants, symbolic integrals, and data points
computed by the graphing commands.
If you suspect a
Calculator cache has become corrupt, you can use the
calc-flush-caches command to reset all caches to the
empty state. (This should only be necessary in the event of bugs
in the Calculator.) The C-x * 0 (with the zero key)
command also resets caches along with all other aspects of the
Calculator's state.