Conclusion

This chapter presents a new path for the construction of (0)^(m)s. By performing contraction earlier than was previously possible, large savings in time can be made for highly contracted integrals. This has the effect of moving previously O(N²) work dependent on K into an O(N) part of the code. The algorithm also uses the BLAS matrix algebra, adding to the efficiency of the implementation. The CO path has been implemented in the Q-CHEM program and shows a three-fold speed up for only moderately contracted (ss|ss) integrals. However, the new algorithm shows a steeper increase in cost with momentum than the more traditional methods, and is seldom faster when the total momentum is greater than four.