random binary matrix with restrictions
I don't think you need any constraint to fulfill the last conditions. Columns = 8, which is just half of 16. You can just simply copy the first 8 rows to the last 8 rows and reverse all the 0 and 1, then the column sum would be 8 and the first three conditions are met.
I want to create a binary 16*15 matrix with certain conditions. I use binary strings to make the matrix. I want my matrix to be as described:
-The first and last two elements of each row must be alternative.
-the sum of each row must be 8 or 7.
-in each row, there should not be consecutive 1s or 0s. (one couple(00 or 11) is allowed in each row) .
-the sum of the columns must be 8.
there are 26 possible strings that can fulfill the first 3 conditions.how can I fulfill the last conditions? 
I have a code but it is not working because it takes so much time and it is almost impossible.is there any other way?