After successfully install postgresql, the default role is postgres. So when you connect postgresql service in your own Ubuntu user, you cannot connect it, reporting the username not in the role. Thus create a role using your own username, and add your username in ROLE of postgres
postgres=# CREATE ROLE ubuntu_username superuser;
postgres=# ALTER ROLE ubuntu_username WITH LOGIN;
I will share some slides being prepared to teach basic C++ to children. C++ is beautiful and useful, particularly when your system has high requirements on efficiency with limited resources. Although high level languages such as Python, are widely used in machine learning, the backbone library is in written in C++ most of times. These slides only include basic C++, not including advanced topics such as class, template, memory management, ……
Practice coding is best way to learning any programming. For each lesson, samples codes are taught. If you are interest, please contact me.