[Piglit] [PATCH] glsl-1.10 / glsl-1.20: Relax precision requirements of variable indexing tests

[Brian Paul]

On 08/21/2013 09:44 PM, Ian Romanick wrote:
> From: Ian Romanick <ian.d.romanick at intel.com>
>
> Many of these tests fail on older GPU such as Intel i915 due to the
> precision requirement.  This is because many GPUs in this class only use
> 24-bit floats.  Many also implement many instructions cheaply (with poor
> precision).
>
> Do a couple things to relax the precision requirement.  First, use the
> distance squared instead of the distance.  This saves an
> inverse-square-root and a multiple.  The inverse-square-root has
> notoriously poor precision on old GPUs.  Second, pick a precision that
> passes on at least one 24-bit float GPU.  I picked 4e-9 because that was
> the smallest bound that would pass on i915.
>
> Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
> ---
> I suspect that r300 GPUs also fail these tests, but I don't have any of
> that hardware around.  Could someone test before and after for me? :)
>
> This is also not the full patch.  The full patch is ~300kb, so the list
> server would have rejected it.  This is just a handful of representitive
> tests and the generator script.
>
>   .../fs-temp-array-mat2-col-row-wr.shader_test             |  4 +++-
>   .../fs-temp-array-mat2-col-wr.shader_test                 |  4 +++-
>   .../fs-temp-array-mat2-index-col-row-wr.shader_test       |  4 +++-
>   .../fs-temp-array-mat2-index-col-wr.shader_test           |  4 +++-
>   .../fs-temp-array-mat2-index-row-wr.shader_test           |  4 +++-
>   .../fs-temp-array-mat2-index-wr.shader_test               |  4 +++-
>   .../vs-temp-array-mat2-col-row-wr.shader_test             |  6 +++---
>   .../vs-temp-array-mat2-col-wr.shader_test                 |  6 +++---
>   .../vs-temp-array-mat2-index-col-row-wr.shader_test       |  6 +++---
>   .../vs-temp-array-mat2-index-col-wr.shader_test           |  6 +++---
>   .../vs-temp-array-mat2-index-row-wr.shader_test           |  6 +++---
>   .../vs-temp-array-mat2-index-wr.shader_test               |  6 +++---
>   tests/spec/glsl-1.10/variable-index-write.sh              | 15 +++++++++++++--
>   13 files changed, 49 insertions(+), 26 deletions(-)
>
> diff --git a/tests/spec/glsl-1.10/execution/variable-indexing/fs-temp-array-mat2-col-row-wr.shader_test b/tests/spec/glsl-1.10/execution/variable-indexing/fs-temp-array-mat2-col-row-wr.shader_test
> index 647cc02..ee9e77f 100644
> --- a/tests/spec/glsl-1.10/execution/variable-indexing/fs-temp-array-mat2-col-row-wr.shader_test
> +++ b/tests/spec/glsl-1.10/execution/variable-indexing/fs-temp-array-mat2-col-row-wr.shader_test
> @@ -16,6 +16,8 @@ uniform int row;
>   uniform int col;
>   uniform float value;
>
> +float distanceSqr(vec a, vec b) { vec diff = a - b; return abs(dot(diff, diff)); }

I believe you can omit the abs().  dot(x,x) will always be >= 0.

-Brian