Integer is a different matter because of truncation. The order is significant.
Floating point is tricky there. the fractional parts can be multiplied in any order in terms of precision. however, the exponents add so best of all would be a kind of alternating summation that keeps them in the +/- 308 range. (1e200 * 1e-199 * 1e180 * 1e-170 and so on). basically...it would be nicer if they were real numbers. :-) On Fri, Aug 18, 2017 at 11:49 AM, John Souvestre <j...@souvestre.com> wrote: > Ø "multiply first, then divide." > > > > While often the right method, I don’t think that it always is. Consider: > > - Integer: It is as long as the product doesn’t overflow (before the > divide). > > - Floating: I’m inclined to think that combining numbers of the same > magnitude first might be a better approach. > > > > John > > John Souvestre - New Orleans LA > > > > *From:* golang-nuts@googlegroups.com [mailto:golang-nuts@googlegroups.com] > *On Behalf Of *Michael Jones > *Sent:* 2017 August 18, Fri 11:50 > *To:* golang-nuts > *Subject:* [go-nuts] multiply and divide > > > > Here is a minor musing from something that came up yesterday. > > > > Sometimes we see a real number expression as simple as... > > > > x*y/z > > > > ...and knowing from basic algebra that... > > > > (x*y)/z == x*(y/z) > > > > ...we might not expect much difference between the two in our code. Alas, > computer floating point does not involve real numbers, rather it uses an > approximation of them. If you will copy https://play.golang.org/ > p/IlDxtvx7IY to your computer, build and run it, (too much CPU for the > playground) you'll find that the order makes a difference. Or, you can just > remember this phrase, "multiply first, then divide." > > > > -- > > Michael T. Jones > michael.jo...@gmail.com > > -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golang-nuts+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > > -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golang-nuts+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- Michael T. Jones michael.jo...@gmail.com -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
