The purpose of this lab is to perform shared-memory tiling by implementing a 7-point stencil.
You will be implementing a 7-point stencil without having to deal
with boundary conditions. The result is clamped so the range is between
the values of 0
and 255
.
for i from 1 to height-1: # notice the ranges exclude the boundary
for j from 1 to width-1: # this is done for simplification
for k from 1 to depth-1:# the output is set to 0 along the boundary
= in(i, j, k + 1) + in(i, j, k - 1) + in(i, j + 1, k) +
res in(i, j - 1, k) + in(i + 1, j, k) + in(i - 1, j, k) -
6 * in(i, j, k)
= Clamp(res, 0, 255)
out(i, j, k) end
end
end
With Clamp
defined as
def Clamp(val, start, end):
return Max(Min(val, end), start)
end
And in(i, j, k)
and out(i, j, k)
are helper
functions defined as
#define value(arry, i, j, k) arry[(( i )*width + (j)) * depth + (k)]
#define in(i, j, k) value(input_array, i, j, k)
#define out(i, j, k) value(output_array, i, j, k)
The most recent version of source code for this lab along with the build-scripts can be found on the Bitbucket repository. A description on how to use the CMake tool in along with how to build the labs for local development found in the README document in the root of the repository.
The executable generated as a result of compiling the lab can be run using the following command:
./Stencil_Template -e <expected.ppm> \
-i <input.ppm> -o <output.ppm> -t image`.
where <expected.ppm>
is the expected output,
<input.ppm>
is the input dataset, and
<output.ppm>
is an optional path to store the
results. The datasets can be generated using the dataset generator built
as part of the compilation process.
The images are stored in PPM (P6
) format, this means
that you can (if you want) create your own input images. The easiest way
to create image is via external tools such as bmptoppm
. The
masks are stored in a CSV format. Since the input is small, it is best
to edit it by hand.