calc: are decimal correct calculations possible?

[mikekaganski]

You try to improve something in “school math”, limiting “school math” to decimals. 1/7 is not a school math, according to you; not something feasible in a day-to-day math. You supply a sample of calculation of 10^5 plus 10^-9, and then talk about “common case” - something you have no idea about. Do you claim you know what “common” case is? please share the stats about cases.

Two times more representable numbers

Of course I’m wrong there; not two times. The specific quotient is of course much more. Yet, this doesn’t change things. The repertoire of numbers representable by base-10 is a tiny fraction of rationals.

[mikekaganski]

1/3 - ‘fractional math’ … we don’t have that in decimals, decimals are a subset of fractionals, we don’t have that in binaries either, they are another subset of fractionals sharing some (few!) values with decimals

… and what you try to do is to make closest possible imperfect representation of those much worse. So the reasonable precision of dealing with those numbers present now will be destroyed. You seem to not understand that at all.

[newbie-02]

@mikekaganski: that’s the point, i understand humans and decimals they feed into a computer as ‘the thing’, and the computer and software … as a tool to help them solving their - mostly decimal - tasks, you understand the computer and the IEEE’s as their own world, and people have to learn to live with it, we won’t get this together, i have the feeling that plenty users, some devs and most people who complain about errors in calc do it from my pov,
15 decimal digits is the claimed ‘range’ where 64-bit doubles hold a series of decimal → binary - decimal conversions, thus the range where reliable math is possible, (it varies depending relation decimal to binary range, 15 digits is lower limit),
school math with fractions is more powerful than decimal math, but most humans use decimals after school, if calc could calculate better with fractions I would use and recommend this immediately, will provide the sheet with user chooseable ranges for the operands shortly …

[newbie-02]

@ajlittoz: ‘In a way, you’re defining an algorithm over the set.’ - yes, may be that describes my understanding and approach, IEEE doubles are a subset of values, and do have a math working inside them, except for a few spinoffs at underflow or overflow, NaN’s and so on, and at cancellation, of which cancellation causes most irritations for users,
if one now takes from this set the ‘subset’ which corresponds with ‘closest representation’ to decimal numbers with 15 significant digits, one can define a mathematics over it which computes somewhat less exactly with irrational values, but within its definition range by rounding artifacts from representation inaccuracies and operations and !cancellation can largely be eliminated, (limited to a ULP of the result!?),

this i would see as the right step to make calc a tool for users to solve everyday tasks instead of a binary adventure guessing and researching why - from the user’s point of view - obviously wrong results are called correct,

[newbie-02]

@mikekaganski: would you consider re-testing your ‘Pythagoras-pi()’ sample with factors of 3*pi() in col. B, and then re-think if this special case of a calculation with an irrational value holding ‘by chance!’ is a justifying argument to block out attempts to make all! calculations with qualified 16 digit decimal values correct?

[mikekaganski]

@newbie-02: would you ever consider re-thinking if it is reasonable to stop spreading lies? Your comment claims that I am blocking something. In fact, I asked you to send your changes to review in gerrit, multiple times. The net result is just blahblahblah, and silly questions like “I’m doing something in source files, I don’t show you but describe in words as if you could get something useful out of it, tell me what specifically should I change”, which I decided to ignore until you follow the advise to use gerrit to discuss stuff.

[newbie-02]

i’m in the process to review and stabilize my changes and sort out garbage, would like to present it in a proper working state to avoid such simple counterarguments as your ‘Pythagoras-pi()’ problem. in theese steps i found it failing with my patches, but failing in standard calc too (with a factor of 3*pi() ). thus if you insist your sample should hold it’s useless - at this state - to look at my work. if you re-consider your sample being allowed to catch small harming from something which improves other results it makes sense to proceed.
‘spreading lies’? - didn’t do,
‘blocking something’? - yes, you blocked my work with the ‘in sheet rounding’ and declared it nonsense based on the Pythagoras-pi() sample, pretending calc would hold for scientific calculations with irrational numbers - which is not true ‘in general’, and ignoring that standard calc already uses massive result rounding in plenty cases.

[mikekaganski]

yes, you blocked my work with the ‘in sheet rounding’

You just did that again. You have asked for discussion, and I provided you with an argument. If you meant “please see how awesome I am, everyone”, and didn’t expect disagreements in answers, then it’s funny. Otherwise, any counter-argument is not a blocker, but just some data to think about, and possibly fix.

Posting unfinished stuff to gerrit is the only way to discuss code changes, e.g. asking how to best fix some code problem. It doesn’t need to be finished.

[newbie-02]

hello @mikekaganski,
if / when you answer to / about ‘the matter’ you are usually very good, when talking about the ‘how to do’ you are often too rough against others and too mimosic about yourself, and we start endless debates.
to avoid that: asking only ‘for the matter’: could a improvement be acceptable if it fails with the ‘Pythagoras-pi()’ problem as calc in standard doe’s similar just with different factors, or is it a blocker?

[mikekaganski]

I suppose that it would be up to @erAck to decide, not me.