Vensim DSS is available in a double precision version that improves computational accuracy, while allowing nearly complete compatibility with the regular Vensim. The double precision version of Vensim can be installed checking on the double precision option when running the installer. The Vensim executable will be named vensimdp.exe and the corresponding Vensim DLL is named vdpdll32.dll. The supporting library files will be installed as part of the regular Vensim installation. Note that the double precision version of Vensim DSS uses separate initialization information from the regular Vensim DSS.
It will work fine to install both the single and double precision versions of Vensim. If you decide to do this, first install the version you do not want models to open with when you click on them in Windows explorer. Then, to use this version, start the program then open the models use File>Open.
We created the double precision version of Vensim in response to requests for decreasing roundoff error. The simulation state is stored in a double precision format while all input and output is done in single precision. For large models the double precision version of Vensim essentially takes twice the memory, so it should be used with discretion. For most business models there seems little to be gained from the added precision.