Changes

== Objectives==

== Steps===== Host Memory Management===In the original program a bmp is loaded into an vector of uint8_t. This is not ideal for CUDA, therefore an array of pinned memory was allocated. This array contains the same amount of elements but stores them as a structure, "BGRPixel" which is three contiguous floats. The vector is then transferred over to pinned memory. === Device Memory Management ===To get a blurred pixel the surrounding pixels must be sampled, in some cases this means sampling pixels outside the bounds of the image. In the original, a simple if check was used to determine if the pixel was outside the bounds or the image, if it was a black pixel was returned instead. This if statement most likely would have caused massive thread divergence in a kernel, therefore the images created in device memory featured additional padding of black pixels to compensate for this. Two such images were created, one to perform horizontal blur and one to perform vertical blur. Other small device arrays were also needed to store the Gaussian integrals that are used to produce the blurring effect.=== Host to Device ===To copy the pinned image to the device an array of streams was used to asynchronously copy each row of the image over. Doing so allowed the rows to be easily copied over while avoiding infringing on the extra padding pixels.=== Kernels ===First one image is blurred horizontally. One image is used as a reference while the other is written to. Kernels are also executed using the streams, so that each stream will blur a single row at a time. After the horizontal blur is finished the vertical blur is launched in the same manner, except that the previously written to image is used as a reference while the previous reference is now written to. The two blur are able to use the same kernel due to the fact that the pixel sampling technique works by iterating through pixels because of this the step size can be changed to sample across the row or down the column. === Device to Host ===After that is down the image is copied back using the streams in the same way it was copied over.