floating point - how to perform high precision calculations in D? -

-

for universitary work have approximate numbers - euler 1 series. therefore have add small numbers, have problems precision. if number ist small doesn't influence result.

real s;  //sum of previous terms ulong k; //factorial  s += 1.0/ k;

after each step, k gets smaller, after 10th round result isn't changeing anymore , stuck @ 2.71828

if need solution run using native types should able reasonable results trying add numbers of similar magnitude. 1 way compute first x terms of series, , repeatedly replace 2 smallest numbers there sum:

auto data = real[n]; foreach(i, ref v; data) {   v = fn(i); }  while(data.length > 1) {   data.sort(); // iirc .sort deprecated forget replaced it.   data[1] += data[0];   data = data[1..$]; }  return data[0];

(a min heap make bit faster.)


Comments

Post a Comment

Popular posts from this blog

python - Scipy curvefit RuntimeError:Optimal parameters not found: Number of calls to function has reached maxfev = 1000 -

-
Image
i want make logharitmic fit. keep getting runtime error: optimal parameters not found: number of calls function has reached maxfev = 1000 i use following script. can tell me go wrong? use spyder still beginner. import math import matplotlib mpl scipy.optimize import curve_fit import numpy np #data f1=[735.0,696.0,690.0,683.0,680.0,678.0,679.0,675.0,671.0,669.0,668.0,664.0,664.0] t1=[1,90000.0,178200.0,421200.0,505800.0,592200.0,768600.0,1036800.0,1371600.0,1630800.0,1715400.0,2345400.0,2409012.0] f1n=np.array(f1) t1n=np.array(t1) plt.plot(t1,f1,'ro',label="original data") # curvefit def func(t,a,b): return a+b*np.log(t) t=np.linspace(0,3600*24*28,13) popt, pcov = curve_fit(func, t, f1n, maxfev=1000) plt.plot(t, func(t, *popt), label="fitted curve") plt.legend(loc='upper left') plt.show() your original data t1 , f1 . therefore curve_fit should given t1 second argument, not t . popt, pcov = curve_fit(func,...
Read more

binding - How can you make the color of elements of a WPF DrawingImage dynamic? -

-
we have need make vector graphic images change color of elements within graphic @ runtime. seem setting colors based on either static or dynamic resource values wouldn't work. want have multiple versions of same graphic, each abilty set graphic elements (path, line, etc) different colors don't think dynamic resource approach work. leaves data binding seems right approach. update graphic use data binding expr instead of hard-coded brush color so: <drawingimage x:key="graphic1"> <drawingimage.drawing> <drawinggroup> <drawinggroup.children> <geometrydrawing geometry="f1 m 8.4073,23.9233l"> <geometrydrawing.pen> <pen linejoin="round" brush="{binding line1brush, mode=oneway}"/> </geometrydrawing.pen> </geometrydrawing> <geometrydrawing geometry="f1 m 3.6875,2.56251l"> <geometrydrawing....
Read more

java - netbeans "Please wait - classpath scanning in progress..." -

-
when try compile netbeans projects message/error : "please wait - classpath scanning in progress..." and nothing happens , have have wait enternity conmpile "hello world"... now first thing have moved new office building, laptop same. it's secure enviroment lot of "security", can't connect anywhere almost. have changed user dir in netbeans.conf save data in c:\program files\user any ideas how fix this? alrady tried reinstalling netbeans, changing save location between standart , newone... just ideas find problem look @ cpu - netbeans busy (100% on 1 core) or blocking (95% idle)? standard, ant or maven build? libraries , use absolute or relative paths? start simple "hello world" project (no dependencies), add 1 lib (log4j or similiar), located in project folder , - if works - move lib other locations (choose locations similiar libs on real classpath) there chance, don't have access rights folders/shares conta...
Read more