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Please read the general instructions for this exercise first. Here are the additional instructions specific to this task:
In this task, the input is always a monochromatic image: each input pixel is either entirely white with the RGB values (1,1,1) or entirely black with the RGB values (0,0,0). Make your solution to IS4 faster by exploiting this property. It is now enough to find a solution for only one color channel, and you will also have much less trouble with rounding errors. In this task, you are permitted to use single-precision floating point numbers.
I will first run all kinds of tests to see that your code works correctly. You can try it out locally by running ./grading test, but please note that your code has to compile and work correctly not only on your own computer but also on our machines.
If all is fine, I will run the benchmarks. You can try it out on your own computer by running ./grading benchmark, but of course the precise running time on your own computer might be different from the performance on our grading hardware.
| Name | Parameters |
|---|---|
| benchmarks/1 | nx = 100, ny = 100 |
| the input is a structured black-and-white image with 100 × 100 pixels | |
| benchmarks/2a | nx = 199, ny = 199 |
| the input is a structured black-and-white image with 199 × 199 pixels | |
| benchmarks/2b | nx = 200, ny = 200 |
| the input is a structured black-and-white image with 200 × 200 pixels | |
| benchmarks/2c | nx = 201, ny = 201 |
| the input is a structured black-and-white image with 201 × 201 pixels | |
| benchmarks/3 | nx = 400, ny = 400 |
| the input is a structured black-and-white image with 400 × 400 pixels | |
| benchmarks/4 | nx = 600, ny = 600 |
| the input is a black-and-white image with 600 × 600 pixels | |
In this task your submission will be graded using benchmarks/4: the input is a black-and-white image with 600 × 600 pixels.
The point thresholds are as follows. If you submit your solution no later than on Sunday, 30 May 2021, at 23:59:59 (Helsinki), your score will be:
| Running time | Points |
|---|---|
| ≤ 8.000 sec | 1 |
| ≤ 5.000 sec | 2 |
| ≤ 3.000 sec | 3 |
| ≤ 2.000 sec | 4 |
| ≤ 1.000 sec | 5 |
If you submit your solution after the deadline, but before the course ends on Sunday, 30 May 2021, at 23:59:59 (Helsinki), your score will be:
| Running time | Points |
|---|---|
| ≤ 5.000 sec | 1 |
| ≤ 3.000 sec | 2 |
| ≤ 1.000 sec | 3 |
Your submissions to this task will also automatically take part in the contest, and you can receive up to 2 additional points if your code is among the fastest solutions this year!
| Running time | Extra points |
|---|---|
| ≤ 1.20 × fastest | 1 |
| ≤ 1.05 × fastest | 2 |