Sign Up to our social questions and Answers Engine to ask questions, answer people’s questions, and connect with other people.
Login to our social questions & Answers Engine to ask questions answer people’s questions & connect with other people.
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Please briefly explain why you feel this question should be reported.
Please briefly explain why you feel this answer should be reported.
Please briefly explain why you feel this user should be reported.
I have just read a question regarding initializing multidimensional vectors (question) and Viktor Sehr and Sbi reccomended instead using a single vector and getting the element with my_vector[x+y*100+z*100*100]. Why is this? Is it for performance reasons? If so, how does it improve performance? Thanks in advance, ell.
Edit: Do these reasons still apply when the width/height/depth are not the same and can change?
Just few reasons:
It wastes spaces, it is slow (unpredictable memory access, cache waste, etc), it’s cumbersome
Main performance drawback is likely to be caching. With flat arrays you are guaranteed memory to be contiguous – cache is happy. With vector of vectors – who knows!