*FLOAT64 Test ~15 sig fig
accuracy! Is "Stardance" affected?
To quote Richard Russell's Help file re this new facility added in BB4W
Version 2.00a Jan 2003:
In *FLOAT40 mode floating-point (real) numbers
have approximately a 9 significant-figure accuracy; in *FLOAT64 mode
they have approximately a 15 significant-figure accuracy. BBC BASIC for Windows
runs no more slowly in *FLOAT64 mode (in fact, it runs more quickly because
it uses the CPU's numeric data processor) but floating-point numeric variables
and arrays occupy more memory.
I thought it would be interesting to test this out using the "Stardance"
program in the demo programs. The test devised tracks a particular star out
to 20,000 screen units and then reports its x-position and the number of program
loops carried out for the 3 star test system to reach this point. (For test's
listing, click here).
Result:
*FLOAT64 1633 loops first x value over
20,000 = 20,002.4841
*FLOAT40 1633 loops first x value over
20,000 = 20,002.4854
It does make a wee difference......65 parts per billion in
this case! Possibly significant though for the future of our universelet.
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