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Reword coalesced exercise README #421

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13 changes: 6 additions & 7 deletions Code_Exercises/Coalesced_Global_Memory/README.md
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Expand Up @@ -14,14 +14,13 @@ coalesced global memory access.
Now that you have a working image convolution kernel you should evaluate whether the
global memory access patterns in your kernel are coalesced.

Consider two alternative ways to linearize the global id:
SYCL buffer & accessor objects can be multi-dimensional, and in this image convolution
example 2d buffer/accessors are used which are operated on in the kernel using a
`sycl::id<2>` 2d index. This operation will
[calculate](https://registry.khronos.org/SYCL/specs/sycl-2020/html/sycl-2020.html#sec:multi-dim-linearization)
the linear address in memory based on the size of the dimensions.

```
auto rowMajorLinearId = (idx[1] * width) + idx[0]; // row-major
auto columnMajorLinearId = (idx[0] * height) + idx[1]; // column-major
```

Try using both of these and compare the execution time of each.
Try inverting the dimensions used in the 2d index and compare the execution time.

## Build and execution hints

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