this simulation stops working after the end moves have been done and the corner moves do not work

1 次查看（过去 30 天）
Vaibhav
Vaibhav 2023-3-13
回答： Rasmita 2023-5-9
clc;
close;
int_polymer=[10 10; 9 10; 8 10; 7 10; 7 9; 8 9; 9 9; 10 9; 10 8; 10 7; 9 7; 9 8; 8 8; 8 7; 7 7; 7 8];
new_polymer =zeros(16,2);
% Create video writer object
writer = VideoWriter('polymer_simulation.mp4','MPEG-4');
writer.FrameRate = 10; % Set the frame rate of the video
open(writer);
% Plot initial state of the polymer
plot(int_polymer(:,1), int_polymer(:,2), 'bo-', 'MarkerSize', 3, 'LineWidth', 2);
title(['interaction energy=',num2str(-1.25*9),' no of steps=',num2str(0),' no of cycles=',num2str(0)]);
grid on;
axis([3 14 4 13]);
set(findobj('type','line'),'XData',int_polymer(:,1),'YData',int_polymer(:,2));
set(findobj('type','scatter'),'XData',int_polymer(:,1),'YData',int_polymer(:,2));
int_ener=-1.25;
Ei=9*int_ener;
no_sim=100000;
kt=1;
for i=1:50
for j=1:no_sim
tpoly=temp_poly(int_polymer);
Et=temp_ener(tpoly)*int_ener;
a=mc_sim(Et,Ei);
if a==1
int_polymer=tpoly;
Ei=Et*int_ener;
end
% Plot current state of the polymer
plot(int_polymer(:,1), int_polymer(:,2), 'bo-', 'MarkerSize', 3, 'LineWidth', 2);
title(['interaction energy=',num2str(Ei),' no of steps=',num2str(j),' no of cycles=',num2str(i)]);
grid on;
axis([3 14 4 13]);
set(findobj('type','line'),'XData',int_polymer(:,1),'YData',int_polymer(:,2));
set(findobj('type','scatter'),'XData',int_polymer(:,1),'YData',int_polymer(:,2));
% Write the current frame to the video file
frame = getframe(gcf);
writeVideo(writer,frame); % Add the current frame to the video file
drawnow;
end
end
close(writer); % Close the video writer object
function tpoly=temp_poly(polymer)
tpoly=polymer;
idx = randi(size(polymer,1));
mono_pos=polymer(idx,:);
allow_choice=0;
if idx==1
choices=[mono_pos(1)+1 mono_pos(2)-1;
mono_pos(1)+1 mono_pos(2)+1;
mono_pos(1)-1 mono_pos(2)+1;
mono_pos(1)-1 mono_pos(2)-1];
for i=1:4
if ((choices(i,1)-polymer(idx+1,1))^2+(choices(i,2)-polymer(idx+1,2))^2)==1
a=ismember(choices(i,:),polymer);
if any(~a)
allow_choice=choices(i,:);
end
end
end
elseif idx==16
choices=[mono_pos(1)+1 mono_pos(2)-1;
mono_pos(1)+1 mono_pos(2)+1;
mono_pos(1)-1 mono_pos(2)+1;
mono_pos(1)-1 mono_pos(2)-1];
for i=1:4
if ((choices(i,1)-polymer(idx-1,1))^2+(choices(i,2)-polymer(idx-1,2))^2)==1
a=ismember(choices(i,:),polymer);
if any(~a)
allow_choice=choices(i,:);
end
end
end
else
choices=[mono_pos(1)+1 mono_pos(2)-1;
mono_pos(1)+1 mono_pos(2)+1;
mono_pos(1)-1 mono_pos(2)+1;
mono_pos(1)-1 mono_pos(2)-1];
for i=1:4
if ((choices(i,1)-polymer(idx+1,1))^2+(choices(i,2)-polymer(idx+1,2))^2)==1&&(choices(i,1)-polymer(idx-1,1))^2+((choices(i,2)-polymer(idx-1,2))^2)==1
a=ismember(choices(i,:),polymer);
if any(~a)
allow_choice=choices(i,:);
end
end
end
end
if allow_choice~=0
tpoly(idx,:)=allow_choice;
end
end
function noofinter=temp_ener(polymer)
noofinter=-15;
distances = pdist(polymer);
for i=1:120
if (distances(i)==1)
noofinter=noofinter+1;
end
end
end
function result=mc_sim(Et,Ei)
del_E = Et - Ei;
r=rand;
w = exp(-del_E);
if w >= 1
result=1;
end
if w < 1
if w > r
result=1;
else
result=0;
end
end
end

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回答（1 个）

Rasmita
Rasmita 2023-5-9
Hi,
As per my understanding, the issue with the provided code is that the algorithm is getting stuck at the end moves of the polymer and the corner moves do not work. This is because there are fewer options to change the position of the monomer. One solution for this issue could be to modify the code to allow the corner moves to take place as well.
Currently, the ‘temp_poly’ function only allows for end moves to be made. To enable corner moves, you could modify this function to consider corner monomers as well. For example, you could add the following code to allow corner moves:
if idx==1 || idx==4 || idx==13 || idx==16 % check if corner monomer
choices=[mono_pos(1)+1 mono_pos(2)+1; mono_pos(1)+1 mono_pos(2)-1; mono_pos(1)-1 mono_pos(2)+1; mono_pos(1)-1 mono_pos(2)-1];
for i=1:4
if ((choices(i,1)-polymer(idx+1,1))^2+(choices(i,2)-polymer(idx+1,2))^2)==1 && ((choices(i,1)-polymer(idx-1,1))^2+(choices(i,2)-polymer(idx-1,2))^2)==1
a=ismember(choices(i,:),polymer);
if any(~a)
allow_choice=choices(i,:);
end
end
end
end
This code checks if the monomer at ‘idx’ is a corner monomer and if so, considers the four choices for the new position. It then checks if the two neighbouring monomers are one unit away from the new position and the new position is not already in the polymer. If there is an allowed choice, ‘tpoly’ is updated accordingly.
With this modification, the polymer simulation should continue to run even after all the end moves have been completed.
Hope this helps!
Regards,
Rasmita

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