If \fIcache\fR is yes and the host machine physical memory and working set size
are large enough, the input image pixels are cached in memory. If cacheing
is enabled and the task is run interactively the first measurement will appear
to take a long time as the entire image must be read in before the measurement
is actually made. All subsequent measurements will be very fast because the task
is accessing memory not disk. The point of cacheing is to speed up random
image access by making the internal image i/o buffers the same size as the
image itself. However if the input object lists are sorted in row order and
sparse cacheing may actually worsen not improve the execution time. Also at
present there is no point in enabling cacheing for images that are less than
or equal to 524288 bytes, i.e. the size of the test image dev$ypix, as the
default image i/o buffer is exactly that size. However if the size of dev$ypix
is doubled by converting it to a real image with the chpixtype task then the
effect of cacheing in interactive is can be quite noticeable if measurements
of objects in the top and bottom halfs of the image are alternated.