
PrecisionTable of contentsThere are two levels of precision that can be utilized in GROMACS  single and double. Both are floatingpoint formats that allow data to occupy different amounts of memory. Single Precision (mixed precision)When installing GROMACS, the default behavior is to utilize single precision. This level of precision is sufficient for most calculations. Note that this is actually mixed precision. The coordinate, velocity and force vectors are single precision, but where necessary, double precision variables are used. A typical example is the accumulation buffer for the virial. In many parts of the code we pay attention to summation order and/or reorder mathematical expressions to avoid rounding errors. Double PrecisionSome techniques, such as Normal Mode Analysis and more thorough energy minimization, require increased precision. To install GROMACS in double precision, set 