Usability of In Situ Generated PDFs for Post Hoc Analysis Scientific Achievement In situ generated probability distribution functions (PDFs) are used to capture large complex simulation trends and store them in an efficient format for post hoc analysis. Significance and Impact Hybrid in situ and post hoc tools enable scientists to interactively study large field and particle-based features. Usability tests with expert users evaluate these tools. A screenshot of the post hoc visualization tool. On the left are three slice views of the spatially distributed PDFs as well as a zoomed in view of a PDF of interest. Selected PDFs are highlighted and are used to query simulation particles, which are shown on the right. Research Details Simulation researchers often need to query large data subsets, sometimes using trial and error, to explore features not known a priori during post hoc analysis. Many methods currently in use by scientific teams inefficiently operate on the full data, necessitating the need for new means of capturing information in situ. A collaboration between the VIDI lab at UC Davis and scientists at Sandia National Laboratory resulted in the development of hybrid in situ/post hoc tools that use spatially distributed PDFs to capture complex simulation phenomena. Large-scale particle data is coupled with PDFs in situ to enable fast subset selection and analysis. A usability study with expert users was completed for the in situ portion and is ongoing for the post hoc portion. Y. Ye, T. Neuroth, F. Sauer, K.-L. Ma, G. Borghesi, A. Konduri, H. Kolla, and J. Chen. In Situ Generated Probability Distribution Functions for Interactive Post Hoc Visualization and Analysis. In Large Data Analysis and Visualization (LDAV), p. 65-74, Oct. 2016.