language agnostic - Is floating point math broken? - 


0.1 + 0.2 == 0.3 -> false 
0.1 + 0.2 -> 0.30000000000000004

why happen?

binary floating point math this. in programming languages, based on ieee 754 standard. javascript uses 64-bit floating point representation, same java's double. crux of problem numbers represented in format whole number times power of two; rational numbers (such 0.1, 1/10) denominator not power of 2 cannot represented.

for 0.1 in standard binary64 format, representation can written as

  • 0.1000000000000000055511151231257827021181583404541015625 in decimal, or
  • 0x1.999999999999ap-4 in c99 hexfloat notation.

in contrast, rational number 0.1, 1/10, can written as

  • 0.1 in decimal, or
  • 0x1.99999999999999...p-4 in analogue of c99 hexfloat notation, ... represents unending sequence of 9's.

the constants 0.2 , 0.3 in program approximations true values. happens closest double 0.2 larger rational number 0.2 closest double 0.3 smaller rational number 0.3. sum of 0.1 , 0.2 winds being larger rational number 0.3 , hence disagreeing constant in code.

a comprehensive treatment of floating-point arithmetic issues what every computer scientist should know floating-point arithmetic. easier-to-digest explanation, see floating-point-gui.de.


-

Comments

Post a Comment

Popular posts from this blog

javascript - Thinglink image not visible until browser resize -

Image
i trying repurpose pre-existing theme, includes drop down menu displays image. trying embed thinglink drop down menu's content section, not visible until resize browser window. here menu looks like: then when clicked, can see empty space image should show: then when browser resized, image appears: this code content of menu: <div class="ajax_accordion_content" style="display: none;"> <div class="report-detail"> <table border="0" cellpadding="0" cellspacing="0" width="100%" class="table_basic"> <tbody> <!-- thinglink image embedded --> <img style="max-width: 100%;" src="http://cdn.thinglink.me/api/image/832705713204625409/1024/10/scaletowidth#tl-832705713204625409;1043138249'" class="alwaysthinglink"/> <script async charset="utf-8" src="http://cdn.thinglink.me/jse/embed.j
Read more

firebird - Error "invalid transaction handle (expecting explicit transaction start)" executing script from Delphi -

i'm developing update app delphi 10. i'm running windows 7 64x, firebird 2.5.1.26351 32x. execution order: checks current version(select statement firebird database) downloads update(via ftp) apply it(.exe files, , execute .sql) error code -901 pops out when try execute .sql files. know there incompatibility issue w7 64x , fdb 32x, but, can everything: backup , restore(gbak), db commands(all). tried fdb 64x instead, , not working. code: //components fdwaitcursor: tfdguixwaitcursor; fddriverlink: tfdphysfbdriverlink; fdconnection:tfdconnection; fdscript: tfdscript; function tthr_script.createcomponents:boolean; begin try fddriverlink := tfdphysfbdriverlink.create(fddriverlink); fdwaitcursor := tfdguixwaitcursor.create(fdwaitcursor); fdconnection := tfdconnection.create(fdconnection); fdconnection begin drivername := 'fb'; params.username := thrbanco.bduser; params.password := thrbanco.bdpass; params.database :=
Read more

mongodb - How to keep track of users making Stripe Payments -

i'm trying figure out way mean stack application keep track of users have paid grant them access portion of webpage. i've considered several options: stripe customer id, mongodb record, , html attribute can update. my mean stack keeps track of users jwt, , appears stripe assigns them own customer id isn't ideal. can done jwt opposed forced cutomer id? mongodb record. i'm thinking might best option. when new user has been created, i'll give attribute of haspaid = no. update record of customer when payment submitted. guess run script set unpaid each day? html element/attribute. don't know if possible; cool create key carried during html session after payment received. if person closers browser session closed? i'm looking guidance on 3 options determine if they're best solution. also, if has suggestions alternatives, i'm ears! thanks in advance. speaking generally, common approach second one: use attribute in data model indicates
Read more