precision - Java double addition rounding off -

-

in java following expression results into

new double(1.0e22) + new double(3.0e22)  = 4.0e22

but

new double(1.0e22) + new double(4.0e22)  = 4.9999999999999996e22

i expecting 5.0e22. double limit 1.7976931348623157e308. appreciate help. machine's architecture x64 , jvm 64 bit.

welcome planet of floating point units. unfortunately, in real world, have give precision speed , breadth of representation. cannot avoid that: double approximate representation. actually, cannot represent number finite precision. still, it's approximation: less 0.00000000001% error. has nothing double upper limits, rather cpu limits, try doing more math python:

>>> 4.9999999999999996 / 5. 1.0 >>> 5. - 4.9999999999999996 0.0

see? side note, never check equality on double, use approximate equality:

if ((a - b) < epsilon)

where epsilon small value. java library has more appropriate, idea.

if insterested in theory, standard floating point operations ieee754


Comments

Post a Comment

Popular posts from this blog

java - Jmockit String final length method mocking Issue -

-
using jmockit 1.2 jar, trying mock string's length method getting unexpected invocation exception: failed: test java.lang.illegalstateexception: missing invocation mocked type @ point; please make sure such invocations appear after declaration of suitable mock field or parameter @ stringdemo.testa$1.<init>(testa.java:17) @ stringdemo.testa.test(testa.java:13) i using testng: @test public void test() throws exception { new expectations() { @mocked("length") string astring; { astring.length(); result = 2; } }; system.out.println(a.showa("test")); } } actual class a: public class { public static int showa(string str){ int a= str.length(); return a; } } this wrong way of recording expected results. shouldn't mock , record string's length() method, record showa() instead. here solution @suppresswarnings("unused&qu
Read more

asp.net - Razor Page Hosted on IIS 6 Fails Every Morning -

-
i have simple page in intranet uses razor/asp fetch single record table , display it, plus few graphic, dashboard display. meaning, no user intervention other first time open ie internal url. the problem having every morning ie displays "page not found or network error" message. refresh page, , it's stuck , doesn't display anything. try different pc, open ie internal url , it's stuck... ...until following: login server hosting page run inetmgr go web sites, etc right click on page that's giving me problem , select browse at moment, error message: server error in '/' application. -------------------------------------------------------------------------------- type of page not served. description: type of page have requested not served because has been explicitly forbidden. extension '.cshtml' may incorrect. please review url below , make sure spelled correctly. requested url: /application/dashboard.cshtml ---------------
Read more

c++ - wxwidget compiling on windows command prompt -

-
can please guide me on method,as how compile wxwidget using windows command prompt or msys. [i can't seem find on wxwiki/wxwidget official book/anywhere else] i have compiled wxwidget instructions have provided (using msys). from searching on internet seems 1 can (maybe?) through use of makefile (is correct?) if yes: directory & how should link wx libraries in makefile if no: way besides makefile? i know can use ide's code::block , make life simpler prefer compile using command prompt/msys. thanks in advance.
Read more