Mixed-Precision Implementation of the Density Matrix Renormalization Group

• DOI: 10.1021/acs.jctc.2c00632
• Publication Date: 2022-11-02T16:12:42Z
• Authors: Yingqi Tian; Zhaoxuan Xie; Zhen Luo; Haibo Ma
• Keywords: 0103 physical sciences; 01 natural sciences

Using the mixed precision strategy to optimize quantum chemistry codes has been proved promising in saving computational cost and maintaining chemical accuracy. Here, an efficient mixed-precision density matrix renormalization group (DMRG) scheme, containing a two-level mixed-precision hierarchy, is developed and demonstrated. At the coarse-grained level, based on the discovery that the single-precision orthogonalization may cause the DMRG generate a totally wrong answer, a feasible single-precision-sweep DMRG method with double-precision orthogonalization process is implemented. At the fine-grained level, a mixed-precision diagonalization algorithm is developed. This algorithm runs specific operations in the single-precision while preserving double-precision accuracy. Combining these two method, a hybrid mixed-precision scheme is presented. By applying this scheme, the DMRG single-point energy calculations are accelerated up to 131%. Mixed-precision DMRG yielded energies are accurate and deviate less than 0.01 kcal/mol compared with standard DMRG calculations.