Attacks on the heap are an increasingly severe threat. State-of-the-art secure dynamic memory allocators can offer protection, however their memory footprint is high, making them suboptimal in many situations. We introduce Slim-Guard, a secure allocator whose design is driven by memory efficiency. Among other features, SlimGuard uses an efficient fine-grain size classes indexing mechanism and implements a novel dynamic canary scheme. It offers a low memory overhead due its size classes optimized for canary usage, its on-demand metadata allocation, and the combination of randomized allocations and over-provisioning into a single memory efficient security feature. SlimGuard protects against widespread heap-related attacks such as overflows, over-reads, double/invalid free, and use-after-free. Evaluation over a wide range of applications shows that it offers a significant reduction in memory consumption compared to the state-of-the-art secure allocator (up to 2x in macro-benchmarks), while offering similar or better security guarantees and good performance.

Illumination is an important way to provide cues for spatial perception, and special lighting models are proposed to illuminate lines in 3D space. To achieve better spatial perception of streamlines, a new streamline illumination method is proposed in this paper, which is based on the fact that a streamline is a sample of a stream surface. In our method, a view-dependent tiny surface passing through the streamline is chosen to compute the line's illumination based on the Phong/Blinn model. Compared with existing line illumination models, our method is more simple and realistic. Test results show that it can enhance spatial perception of streamlines significantly.

Parallel streamline placement is still an open problem in flow visualization. In this paper, we propose an innovative method to place streamlines in parallel for 2D flow fields. This method is based on our proposed concept of local tracing areas (LTAs). An LTA is defined as a subdomain enclosed by streamlines and/or field borders, where the tracing of streamlines are localized. Given a flow field, it is initialized as an LTA, which is later recursively partitioned into hierarchical LTAs. Streamlines are placed within different LTAs simultaneously and independently. At the same time, to control the density of streamlines, each streamline is associated with an isolation zone and a saturation zone, both of which are center aligned with the streamline but have different widths. None of streamlines can trace into isolation zones of others. And new streamlines are only seeded within valid seeding areas (VSAs) that are enclosed by saturation zones and/or field borders. To implement the parallel strategy and the density control, a cell-based modeling is devised to describe isolation zones and LTAs as well as saturation zones and VSAs. With the help of these cell-based models, a heuristic seeding strategy is proposed to seed streamlines within irregular LTAs, and a cell-marking technique is used to control the seeding and tracing of streamlines. Test results show that the placement method can achieve highly parallel performance on shared memory systems without losing the quality of placements.