Stefan Hannie Email & Phone Number

Vancouver, Bc, Ca

Vancouver, British Columbia, Canada

Vancouver, British Columbia, Canada

Burnaby, Bc

◣ Contributed to the open-source project minorminer. (Python, Metric spaces, Graph drawing) ⊿ Designed, implemented, tested, and documented several class-based layout & placement algorithms. ⊿ Improved minorminer–lowered runtime and increased success and minor quality. ⊿ Most recent pull request: https://github.com/dwavesystems/minorminer/pull/121◣ Algorithms research for finding graph minors. (Python, Integer Programming, Partitioning) ⊿ Formulated and… Show more ◣ Contributed to the open-source project minorminer. (Python, Metric spaces, Graph drawing) ⊿ Designed, implemented, tested, and documented several class-based layout & placement algorithms. ⊿ Improved minorminer–lowered runtime and increased success and minor quality. ⊿ Most recent pull request: https://github.com/dwavesystems/minorminer/pull/121◣ Algorithms research for finding graph minors. (Python, Integer Programming, Partitioning) ⊿ Formulated and implemented a novel graph minor integer linear program using PythonMIP. ⊿ Researched algorithms utilizing graph quotients and graph partitions, i.e. METIS & Kernighan-Lin. Show less

Vancouver, Canada Area

◣ Echo Location: IP address geolocation. (Python, Websockets, Multiprocessing, Linear Programming) ⊿ Multiprocessing design: runs an API server, iteratively solves an LP, and ingests traceroutes via websocket. ⊿ Uses the traceroutes to build a directed graph and the linear program to solve for edge weights.◣ Ranger: a microservice for Echo Location. (Python, Redis Pub/Sub, Multiprocessing) ⊿ Parses data for important IP addresses and issues traceroutes to them via… Show more ◣ Echo Location: IP address geolocation. (Python, Websockets, Multiprocessing, Linear Programming) ⊿ Multiprocessing design: runs an API server, iteratively solves an LP, and ingests traceroutes via websocket. ⊿ Uses the traceroutes to build a directed graph and the linear program to solve for edge weights.◣ Ranger: a microservice for Echo Location. (Python, Redis Pub/Sub, Multiprocessing) ⊿ Parses data for important IP addresses and issues traceroutes to them via Ripe Atlas. ⊿ Interact with Echo Location via REST to geolocate IP addresses and aid in graph construction.◣ Polaris: a user portal web app for VoIP customers. (Python, Typescript, Vue.js, Redis, CockroachDB) ⊿ A user portal integrating live calls, call history, a web dialer, visual voicemail, a contact list, and settings. ⊿ Designed and implemented a scalable relational database schema to support endless integrations.◣ Concierge: a single user onboarding web app utilizing the Polaris stack. (Typescript, Vue.js) ⊿ Queries several APIs to find an available VoIP number for purchase. ⊿ Creates a Polaris user and all associated external users. Show less

Vancouver, British Columbia, Canada

Performed the underlying research for developing Echo Location (see above).

Vancouver, Canada Area

◣ Created visualizations. (Python, Javascript, D3.js, Echarts) ⊿ Created visuals for associating traceroutes to VoIP calls. ⊿ Created visuals for account metrics based on account hierarchy. ⊿ Experimented with time series database InfluxDB and graph database Neo4j.

Vancouver, British Columbia, Canada

A 2-regular digraph is one where every vertex has in-degree and out-degree 2. My thesisfocuses on surface embeddings of 2-regular digraphs, one where the underlying graph isembedded in a surface and all faces are bounded by directed closed walks. Immersion actsas a natural minor-like containment relation for embedded 2-regular digraphs and thistheory is linked to undirected graph minors by way of the directed medial graph.In my thesis, I parallel the theory of undirected… Show more A 2-regular digraph is one where every vertex has in-degree and out-degree 2. My thesisfocuses on surface embeddings of 2-regular digraphs, one where the underlying graph isembedded in a surface and all faces are bounded by directed closed walks. Immersion actsas a natural minor-like containment relation for embedded 2-regular digraphs and thistheory is linked to undirected graph minors by way of the directed medial graph.In my thesis, I parallel the theory of undirected graphs in surfaces by proving analogues of Whitney’s Theorem and Tutte’s peripheral cycles theorem for 2-regular digraphs in the sphere. Then, using a notion of branch-width and a 2-regular digraph grid theorem by Johnson, I prove that for each fixed surface S, the 2-regular digraphs embeddable in S are characterized by a finite list of immersion obstructions. I then present the current state of the art with regard to classification of obstructions for surfaces: Johnson characterized the sphere obstructions, we classify all projective plane obstructions, and we have a computer assisted partial list of obstructions for the torus and Klein bottle.In my thesis, I also consider two open problems in the world of undirected graphs on surfaces and resolve their analogues in the world of 2-regular digraphs on surfaces. The first conjecture by Negami we resolve in the affirmative, that a 2-regular digraph has a finite planar cover if and only if it is projective planar. The second, the strong embedding conjecture, is resolved in the negative and we provide an infinite family of well connected counter-examples. Show less

Vancouver, British Columbia, Canada

I have been a Teaching Assistant for various courses including Topology, Set Theory, Ordinary Differential Equations, and Undergraduate Seminar: Euclidean and Non-Euclidean Geometries. I've also been appointed to drop-in style workshops that cover the courses of Linear Algebra, Discrete Mathematics, Pre-Calculus, Foundations of Analytical and Quantitative Reasoning, and Mathematics for Teachers. My duties include the creation and performance of weekly tutorials, holding a weekly office… Show more I have been a Teaching Assistant for various courses including Topology, Set Theory, Ordinary Differential Equations, and Undergraduate Seminar: Euclidean and Non-Euclidean Geometries. I've also been appointed to drop-in style workshops that cover the courses of Linear Algebra, Discrete Mathematics, Pre-Calculus, Foundations of Analytical and Quantitative Reasoning, and Mathematics for Teachers. My duties include the creation and performance of weekly tutorials, holding a weekly office hour, marking assignments, and facilitating a relationship between the students and their professor. Show less

Doctor Of Philosophy (Ph.D.), Discrete Mathematics - Graph Theory

Bachelor’S Degree, Mathematics And Computer Science