<| For something that 'of course', Google shows well over 80,000 hits for
| "machine precision". Maybe they're all cruft, but a lot of them seem
| to be hosted by universities. What do you know that the professors
| involved don't?

OK, If that is the general meaning of the term, then I accept that of course. I'm certainly not going to check all your 80,000
hits to check that they really are professors.........
I just pointed out (not that you didn't know), that the machine can be programmed to any precision. And IEEE is certainly not the
only built-in limited precision calculation algorithm.

<| This may work in this case, but sometimes the significant digits are
| further away from the decimal point. If the highest/lowest order
| significant digit were 12 decimal places away from the decimal point,
| you're going to have trouble with the maximum change entry

You're right. Certainly in this example.
In my own models I never goalseek the result to a value, I always goalseek the fractional difference between result and goal to be
zero. If you do that with 0.000000000000001 for Maximum change, you may need a few more iterations, but you'll be as close as is
possible within the IEEE limitations.


--
Kind regards,

Niek Otten
Microsoft MVP - Excel



"Harlan Grove" wrote in message ...
| "Niek Otten" wrote...
| <maximum change can't be set to machine precision
|
| Of course there is no such thing as "machine precision", but I used
| your words because it's a nice way to describe precision of the
| algorithms used.
|
| Machine precision means, in the case of IEEE double precision floating
| point, numbers that can be represented exactly using 1 sign bit, 11
| bits for the base-2 order and 52 bits for the base-2 fractional part.
|
| For something that 'of course', Google shows well over 80,000 hits for
| "machine precision". Maybe they're all cruft, but a lot of them seem
| to be hosted by universities. What do you know that the professors
| involved don't?
|
| If I set Maximum change to 0.000000000000001 I get the same answer
| as with your formula, in both cases (using Excel) with same number
| of significant digits: 1.42857142857143. . . .
| ...
|
| This may work in this case, but sometimes the significant digits are
| further away from the decimal point. If the highest/lowest order
| significant digit were 12 decimal places away from the decimal point,
| you're going to have trouble with the maximum change entry.