Using ssim() function for contour map comparisons

I have a lot of contour maps for instance lets say 2000. I have to compare two images and get their ssim value. I am going to define a value eg. 0.9 and if the value is more than that I want to group them in one cluster otherwise separate them. So basically I want to make clusters by grouping these contours and I can define those values to be 0.9 or other values. Suppose I have four values 0.6,0.7,0.8,0.9. I will use ifelse to group them into these 5 interval groups. For doing this I will have to compare each image with the other but I think if I use loop the computational time would be very much and since it is MATLAB I think vectors and arrays would be a better option. Please help me how can I achieve that. I am including a code section. Here A and B are the first two images and also if you could let me know that how it would be less computational cost to read the images in a different style with the case that I have nearly 2000 images. Thanks in advance.

A=imread('33049-33568.jpg');
B=imread('58893-59180.jpg');
[ssimval, ssimmap] = ssim(B,A);
fprintf('The SSIM value is %0.4f.\n',ssimval);