How do I translate "large-scale optimization problem" to Spanish language? I'm writting my PhD thesis in Spanish, and I need to know how to write "large-scale optimization problem" to Spanish language. If additionally you could give a refence for that translation, I would be very glad.

You could use Google Translator for that. Just type English to Spanish in Google and you will find many. In Spanish "large-scale optimization problem" means " **Problema de optimización a gran escala** "