Canadian Traveller Problem

Given an instance, a description of how to follow the instance in the best way is called a policy. The CTP task is to compute the expected cost of the optimal policies. To compute an actual description of an optimal policy may be a harder problem. Given an instance and policy for the instance, every realization produces its own (deterministic) walk in the graph. Note that the walk is not necessarily a path since the best strategy may be to, e.g., visit every vertex of a cycle and return to the start. This differs from the shortest path problem (with strictly positive weights), where repetitions in a walk implies that a better solution exists. There are primarily five parameters distinguishing the number of variants of the Canadian Traveller Problem. The first parameter is how to value the walk produced by a policy for a given instance and realization. In the Stochastic Shortest Path Problem with Recourse, the goal is simply to minimize the cost of the walk (defined as the sum over all edges of the cost of the edge times the number of times that edge was taken).  This c on᠎tent　has ᠎been ​done ᠎with G᠎SA C᠎onte nt Gene​rato᠎r DEMO.

The case study was divided into five sections, the last of which was only tested on the AB exam. Roughly five multiple-choice questions in Section I were devoted to the GridWorld Case Study, and it was the topic of one free response question in Section II. GridWorld has been discontinued and replaced with a set of labs for the 2014-2015 school year. Actors - The GridWorld Case Study employs an Actor class to construct objects in the grid. The Actor class manages the object's color, direction, location, what the object does in the simulation, and how the object interacts with other objects. Actors are broken down into the classes "Flower", "Rock", "Bug", and "Critter", which inherit the Actor class and often override certain methods (most notably the Act method). Flowers can't move, and when forced to Act, they become darker. Flowers are dropped by Bugs and eaten by Critters. Rocks are also immobile and aren't dropped or eaten.

In 1999, researchers led by Yang Dan at the University of California, Berkeley decoded neuronal firings to reproduce images seen by cats. The team used an array of electrodes embedded in the thalamus (which integrates all of the brain's sensory input) of sharp-eyed cats. Researchers targeted 177 brain cells in the thalamus lateral geniculate nucleus area, which decodes signals from the retina. The cats were shown eight short movies, and their neuron firings were recorded. Using mathematical filters, the researchers decoded the signals to generate movies of what the cats saw and were able to reconstruct recognizable scenes and moving objects. Similar results in humans have since been achieved by researchers in Japan (see below). Miguel Nicolelis, a professor at Duke University, in Durham, North Carolina, has been a prominent proponent of using multiple electrodes spread over a greater area of the brain to obtain neuronal signals to drive a BCI.

By the late 1950s the macro language was followed by the Macro Assemblers. This was a combination of both where one program served both functions, that of a macro pre-processor and an assembler in the same package. McIlroy's 1960 paper was seminal in the area of extending any (including high-level) programming languages through macro processors. Macro Assemblers allowed assembly language programmers to implement their own macro-language and allowed limited portability of code between two machines running the same CPU but different operating systems, for example, early versions of MSDOS and CPM-86. The macro library would need to be written for each target machine but not the overall assembly language program. Note that more powerful macro assemblers allowed use of conditional assembly constructs in macro instructions that could generate different code on different machines or different operating systems, reducing the need for multiple libraries. In the 1980s and early 1990s, desktop PCs were only running at a few MHz and assembly language routines were commonly used to speed up programs written in C, Fortran, Pascal and others.