How can I execute my Thomas Algorithm function using Matlab? -


i have created function execute thomas algorithm. i'm trying use function solve system following arrays:

b = -4ε + 2αh^2

a = 2ε - h(1+α(n+1)h)

c = 2ε + h(1+αnh)

g = 4kπh^2sin(kπnh)

where α=1.2, k=2, ε=0.02, r=4

i've inserted function (below), i'm not sure how enter in these parameters in command window i'm pretty new matlab. appreciated.

function y = thomasalgorithm(a,b,c,f)    % obtain values    m = length(f);      f(1) = f(1)/b(1);      % forward substitution      j = 1:m-1          c(j) = c(j)/b(j);          b(j+1) = b(j+1) - a(j)*c(j);          f(j+1) = (f(j+1) - a(j)*f(j))/b(j+1);      end;      % backwards substitution      k = m-1:-1:1          f(k) = f(k) - c(k)*f(k+1);      end;      % output      y = f;   end

i tried put command window (below) got error:

error in thomasalgorithm (line 11)        b(j+1) = b(j+1) - a(j)*c(j);

i'm not sure i'm going wrong @ moment or how solve , i've kind of hit wall. 

>> m=10; x0=0, xm=1; y0=r, ym=0; alpha=1.2; k=2; eps=0.02; r=4; h=xm-x0/m; a=[2*eps-h*(1+alpha*((1:m-1)+1)*h)]; b=[-4*eps+2*alpha*h*h]; c=[2*eps+h*(1+(alpha*(1:m-1)*h))]; f=[4*k*pi*h*h*sin(k*pi*(1:m-1)*h)]; x=thomasalgorithm(a,b,c,f); ic=1:n disp(x); end

put of stuff you've put in command window separate script (.m file) instead, run it. allows actual full error message, , keeps command window clutter free!

when running script code in, see following error:

undefined function or variable 'r'.
error in myscript (line 3)
y0=r, ym=0;

now (first) problem clear! set y0=r when r doesn't exist. it's practise @ times run clear before run script, workspace emptied , know you've not defined in script.

so add r = 1 or start, run again. now have indexing error!

index exceeds matrix dimensions.
error in thomasalgorithm (line 8)
b(j+1) = b(j+1) - a(j)*c(j);

this because defined b 

b=[-4*eps+2*alpha*h*h]; % scalar not vector!

then passed thomasalgorithm , expected able index it, when isn't vector.

hopefully points out immediate problem, , how better diagnose issues. when code in script can step through it debug things.


Comments

Post a Comment

Popular posts from this blog

Is there a better way to structure post methods in Class Based Views -

i'm using class based views in django , never specify url in ajax calls , omit action parameter in form because know these requests go through post method of class based view. notice view - profile page make many requests depending on user updating on page - post method become convoluted , if/else mess example: def post(self, request, *args, **kwargs): # handle user changing available date if request.post.get('availabledate') != none: self.updateavailabledate(request) return jsonresponse({'result':'success'}) if request.post.get('newprojectname') != none: creative_user = creativeuserprofile.objects.get(id = request.user.id) project = project.create_project(creative_user, request.post['newprojectname']) project.save() return jsonresponse({'projectid': project.id }) if request.post.get('projectimage') != none , request.files['file']: proj
Read more

performance - Why is XCHG reg, reg a 3 micro-op instruction on modern Intel architectures? -

i'm doing micro-optimization on performance critical part of code , came across sequence of instructions (in at&t syntax): add %rax, %rbx mov %rdx, %rax mov %rbx, %rdx i thought had use case xchg allow me shave instruction , write: add %rbx, %rax xchg %rax, %rdx however, dimay found agner fog's instruction tables , xchg 3 micro-op instruction 2 cycle latency on sandy bridge, ivy bridge, broadwell, haswell , skylake. 3 whole micro-ops , 2 cycles of latency! 3 micro-ops throws off 4-1-1-1 cadence , 2 cycle latency makes worse original in best case since last 2 instructions in original might execute in parallel. now... cpu might breaking instruction micro-ops equivalent to: mov %rax, %tmp mov %rdx, %rax mov %tmp, %rdx where tmp anonymous internal register , suppose last 2 micro-ops run in parallel latency 2 cycles. given register renaming occurs on these micro-architectures, though, doesn't make sense me done way. why wouldn't register renamer
Read more

jquery - Responsive Navbar with Sub Navbar -

good day, forgive me nav vocabulary not best. if question confusing apologize. i'm working on navigation bar needs centered on page @ 768px , above. items in nav open (or perhaps toggle) subnav lives directly below. these nav should appear centered on page. i have been able work through responsive portion of nav bar, having main items align vertically , sub nav menu of each item roll out below, , gave them indent separation. working well. however, issue not responsive side, behavior @ width greater 768px. happens toggling menu's sub navigation pushes other main items down page below sub nav. here's code: $(document).ready(function () { //stick in fixed 100% height behind navbar don't wrap $('#slide-nav.navbar-inverse').after($('<div class="inverse" id="navbar-height-col"></div>')); $('#slide-nav.navbar-default').after($('<div id="navbar-height-col"></d
Read more