CODEWITHSUNDEEP
matlabmatlab-figure
James
James

Reputation: 127

How to speed up the plotting of graphs using pause()?

I understand that when plotting an equation for x iterations that when you use a pause with a decimal number you can speed up the time it takes to go from one iteration to the next. My question is there a way to speed it up even more? Basically I am running a upwind 1D advection equation and my plot is doing pretty slow even when I put a pause of say 0.0001. Any advice on making the speed of this program increase for plotting or would I just need to let it run its course. Here is the code I am using:

clear;
clc;
%Set initial values
xmin=0; 
xmax=1;
N=101; %Amount of segments
dt= 0.0001; % Time step
t=0; % t initial
tmax=2; % Run this test until t=2
u=1; %Velocity

dx = (xmax - xmin)/100 %finding delta x from the given information
x =xmin-dx : dx : xmax+dx; %setting the x values that will be plugged in

h0= exp(-(x- 0.5).^2/0.01); %Initial gaussian profile for t=0
h = h0;
hp1=h0;
nsteps =tmax/dt; % total number of steps taken
for n=1 : nsteps
    h(1)=h(end-2); %Periodic B.C
    h(end)=h(2);

    for i =2 : N+1
        if u>0

            hp1(i) = h(i) - u*dt/dx *( h(i)-h(i-1)); %Loop to solve the FOU
        elseif u<0
            hp1(i) = h(i) - u*dt/dx*(h(i+1)-h(i)); %downwind
        end

    end

    t=t+dt; %Increase t after each iteration
    h= hp1; %have the new hp1 equal to h for the next step
    initial= exp(-(x- 0.5).^2/0.01); % The initial plot when t =0
    %hold on
    plot(x,initial,'*') %plot initial vs moving
    plot(x,h,'o-')
    pause(0.0001);
    %hold off

    figure(2)
    plot(x,initial) %plot end value
end

Upvotes: 0

Views: 353

Answers (1)

Anders Sandberg
Anders Sandberg

Reputation: 126

Isn't this "speedup" due to pause() flushing the graphic event buffer like drawnow, but apparently doing it faster? So it is not the length of the pause doing any work (in fact, I don't think the resolution is in the millisecond range on many machines) but just the command itself.

The thing really slowing down your code is those for loops. You should try to change the code to calculate the segments in parallel instead.

Upvotes: 1

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