  The demands of cutting-edge science are driving the need for larger and
faster computing resources. With the rapidly growing scale of computing systems
and the prospect of technologically disruptive architectures to meet these
needs, scientists face the challenge of effectively using complex computational
resources to advance scientific discovery. Multidisciplinary collaborating
networks of researchers with diverse scientific backgrounds are needed to
address these complex challenges. The UNEDF SciDAC collaboration of nuclear
theorists, applied mathematicians, and computer scientists is developing a
comprehensive description of nuclei and their reactions that delivers maximum
predictive power with quantified uncertainties. This paper describes UNEDF and
identifies attributes that classify it as a successful computational
collaboration. We illustrate significant milestones accomplished by UNEDF
through integrative solutions using the most reliable theoretical approaches,
most advanced algorithms, and leadership-class computational resources.
