It's still good to switch from computational mathematics to computer, because you are majoring in mathematics, and the foundation of mathematics should be better than that of computer department, and you have received good logic training for four years. Instructors in the computer department also like to recruit students from the mathematics department.

Math scores were very cheap when taking the postgraduate entrance examination. Just spend some time in English and professional classes. Many of my classmates transferred from the postgraduate entrance examination for computational mathematics to computers.

Wish the postgraduate entrance examination go smoothly!