c++ - Ensure float to be smaller than exact value -

-

i want calculate sum of following form in c++ 

float result = float(x1)/y1+float(x2)/y2+....+float(xn)/yn

xi,yi integers. result approximation of actual value. crucial approximation smaller or equal actual value. can assume values finite , positive. tried using nextf(,0) in code snippet.

cout.precision( 15 ); float = 1.0f / 3.0f * 10; //3 1/3 float b = 2.0f / 3.0f * 10; //6 2/3 float af = nextafterf( , 0 ); float bf = nextafterf( b , 0 ); cout << << endl; cout << b << endl; cout << af << endl; cout << bf << endl; float sumf = 0.0f; ( int = 1; <= 3; i++ ) {     sumf = sumf + bf; } sumf = sumf + af; cout << sumf << endl;

as 1 can see correct solution 3*6,666... +3.333.. = 23,3333... output get:

3.33333349227905 6.66666698455811 3.33333325386047 6.66666650772095 23.3333339691162

even though summands smaller should represent, sum not. in case applying nextafterf sumf give me 23.3333320617676 smaller. work? possible rounding error gets big nextafterf still leaves me above correct value?

i know avoid implementing class fractions , calculating exactly. i'm curious whether possible achieve goal floats.

try changing float rounding mode fe_towardzero.

see code example here:

change floating point rounding mode


Comments

Post a Comment

Popular posts from this blog

html - Firefox flex bug applied to buttons? -

-
i'm trying apply flex button on firefox i'm having problem on chrome doesn't happens. this css: .button { display: inline-flex; align-items: center; } as can see in fiddle, "caret" word moved new line, happens if element <button> tag, <div> works expected. http://codepen.io/anon/pen/xblmgx is firefox bug or there css i'm missing? nevermind, looks "mr firefox" doesn't idea... <button> not implementable (by browsers) in pure css, bit of black box, perspective of css. means don't react in same way e.g. <div> would. this isn't specific flexbox -- e.g. don't render scrollbars if put "overflow:scroll" on button, , don't render table if put "display:table" on it. stepping further, isn't specific <button> . consider <fieldset> , <table> have special rendering behavior: data:text/html,<fieldset style="d
Read more

html - Missing border-right in select on Firefox -

-
Image
when put select div width , padding-left, options have no border on right. more, happend if select have width 118px , parent have 15px of padding left! have idea, going on? my code: <!doctype html> <html> <head lang="en"> </head> <body> <div style="width: 1000px; padding-left: 15px;"> <select style="width: 118px;"> <option>a</option> <option>b</option> <option>c</option> </select> </div> </body> </html> and result: here plunker: click it happend on firefox on windows. tested on 40.0.2 version -webkit-box-sizing: border-box; -moz-box-sizing: border-box; -ms-box-sizing: border-box; box-sizing: border-box; source: https://stackoverflow.com/a/11390432/4431269 source of problem: https://bugzilla.mozilla.org/show_bug.cgi?id=924068 and use of google ! edit: (source of problem, explained) after rea
Read more

c# - two queries in same method -

-
i trying execute 2 queries in same method gives me exception. can red of exception declaring new command there way use same command? string id="hi"; connection.open(); oledbcommand command1 = new oledbcommand(); command1.connection = connection; string query1 = "select * products category='" + combobox1.text + "' , subcategory = '" + combobox2.text + "' , sizes='" + combobox3.text + "'"; command1.commandtext = query1; oledbdatareader reader = command1.executereader(); while (reader.read()) { id = reader[0].tostring(); } textbox1.text = id; string query = "insert category_in (category_id,amount,amount_in) values ('"+ id+"' ,500,300)"; command1.commandtext = query; command1.executenonquery(); messagebox.show("saved"); connection.close();
Read more