[PATCH 0/2] MR224: tests: Test coarse and fine derivates and demand less precision from ddx() and ddy().

[Francisco Casas (＠fcasas)]

On my Nvidia GeForce GTX 1050 Ti `ddxddy.shader_test` doesn't pass because of considerably different numeric results.

As Giovanni pointed out, this is because my GPU uses the fine derivate and not the coarse derivate to implement ddx() and ddy().

For this reason, the result for ddx|ddy() is quantized so that the test passes if the GPU uses either coarse or fine derivates.

Additionally, tests for both ddx_coarse|ddy_coarse() and ddx_fine|ddy_fine() are added, that expect a more precise result.

[PATCH 1/2] tests: Test coarse and fine derivates.

[Francisco Casas]

From: Francisco Casas

---
 tests/ddxddy.shader_test | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/tests/ddxddy.shader_test b/tests/ddxddy.shader_test
index 6efb5ab6f..371bb85ff 100644
--- a/tests/ddxddy.shader_test
+++ b/tests/ddxddy.shader_test
@@ -24,3 +24,43 @@ probe (10, 11) rgba (-0.420000076, -0.164999843, 0.104999900, 0.0) 8
 probe (11, 11) rgba (-0.574999928, -0.164999843, 0.104999900, 0.0) 8
 probe (12, 10) rgba (-0.874999881, -0.205000162, 0.124999881, 0.0) 8
 probe (150, 150) rgba (-7.52500916, -1.56500244, 1.50500488, 0.0) 40
+
+
+[require]
+shader model >= 5.0
+
+
+[pixel shader todo]
+float4 main(float4 pos : sv_position) : sv_target
+{
+    pos /= 10.0;
+    float nonlinear = pos.x * pos.y - pos.x * (pos.x + 0.5);
+    return float4(nonlinear, ddx_coarse(nonlinear), ddy_coarse(nonlinear), 0.0);
+}
+
+[test]
+todo draw quad
+probe (10, 10) rgba (-0.524999976, -0.164999843, 0.104999900, 0.0) 8
+probe (11, 10) rgba (-0.689999819, -0.164999843, 0.104999900, 0.0) 8
+probe (10, 11) rgba (-0.420000076, -0.164999843, 0.104999900, 0.0) 8
+probe (11, 11) rgba (-0.574999928, -0.164999843, 0.104999900, 0.0) 8
+probe (12, 10) rgba (-0.874999881, -0.205000162, 0.124999881, 0.0) 8
+probe (150, 150) rgba (-7.52500916, -1.56500244, 1.50500488, 0.0) 40
+
+
+[pixel shader todo]
+float4 main(float4 pos : sv_position) : sv_target
+{
+    pos /= 10.0;
+    float nonlinear = pos.x * pos.y - pos.x * (pos.x + 0.5);
+    return float4(nonlinear, ddx_fine(nonlinear), ddy_fine(nonlinear), 0.0);
+}
+
+[test]
+todo draw quad
+probe (10, 10) rgba (-0.524999976, -0.164999843, 0.104999900, 0.0) 8
+probe (11, 10) rgba (-0.689999819, -0.164999843, 0.114999890, 0.0) 8
+probe (10, 11) rgba (-0.420000076, -0.154999852, 0.104999900, 0.0) 8
+probe (11, 11) rgba (-0.574999928, -0.154999852, 0.114999890, 0.0) 8
+probe (12, 10) rgba (-0.874999881, -0.205000162, 0.124999881, 0.0) 8
+probe (150, 150) rgba (-7.52500916, -1.56500244, 1.50500488, 0.0) 40

[PATCH 2/2] tests: Quantize ddx() and ddy() test.

[Francisco Casas]

From: Francisco Casas

---
 tests/ddxddy.shader_test | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/tests/ddxddy.shader_test b/tests/ddxddy.shader_test
index 371bb85ff..8e68ce587 100644
--- a/tests/ddxddy.shader_test
+++ b/tests/ddxddy.shader_test
@@ -1,3 +1,7 @@
+% NOTE: Only allowed from shader model ps_2_1
+[require]
+shader model >= 4.0
+
 [pixel shader]
 float4 main(float4 pos : sv_position) : sv_target
 {
@@ -13,17 +17,21 @@ float4 main(float4 pos : sv_position) : sv_target
 {
     pos /= 10.0;
     float nonlinear = pos.x * pos.y - pos.x * (pos.x + 0.5);
-    return float4(nonlinear, ddx(nonlinear), ddy(nonlinear), 0.0);
+    float4 res = float4(nonlinear, ddx(nonlinear), ddy(nonlinear), 0.0);
+
+    // Each device may use either the coarse or the fine derivate, so use quantization.
+    return round(30 * res);
 }

[test]
 draw quad
-probe (10, 10) rgba (-0.524999976, -0.164999843, 0.104999900, 0.0) 8
-probe (11, 10) rgba (-0.689999819, -0.164999843, 0.104999900, 0.0) 8
-probe (10, 11) rgba (-0.420000076, -0.164999843, 0.104999900, 0.0) 8
-probe (11, 11) rgba (-0.574999928, -0.164999843, 0.104999900, 0.0) 8
-probe (12, 10) rgba (-0.874999881, -0.205000162, 0.124999881, 0.0) 8
-probe (150, 150) rgba (-7.52500916, -1.56500244, 1.50500488, 0.0) 40
+probe (10, 10) rgba (-16.0, -5.0, 3.0, 0.0)
+probe (11, 10) rgba (-21.0, -5.0, 3.0, 0.0)
+probe (10, 11) rgba (-13.0, -5.0, 3.0, 0.0)
+probe (11, 11) rgba (-17.0, -5.0, 3.0, 0.0)
+probe (12, 10) rgba (-26.0, -6.0, 4.0, 0.0)
+probe (16, 16) rgba (-25.0, -7.0, 5.0, 0.0)
+probe (150, 150) rgba (-226.0, -47.0, 45.0, 0.0)

[require]

[Zebediah Figura (＠zfigura)]

Zebediah Figura (@zfigura) commented about tests/ddxddy.shader_test:
> +% NOTE: Only allowed from shader model ps_2_1
> +[require]
> +shader model >= 4.0

That would be unfortunate, do we really need this?

[Francisco Casas (＠fcasas)]

On Tue Jun  6 17:57:18 2023 +0000, Zebediah Figura wrote:
> That would be unfortunate, do we really need this?

Well, only if we want to keep the crosstests from failing.
```
shader_runner:1237: Running tests from a Windows cross build
shader_runner:1239: Compiling shaders with d3dcompiler_47.dll and executing with d3d9.dll
shader_runner:95: Driver string: d3d10warp.dll.
shader_runner:96: Device: Microsoft Basic Render Driver, 1414:008c.
shader_runner:99: Using WARP device.
shader_runner:73: Section [test], line 9: Test failed: Failed to compile shader, hr 0x80004005.
shader_runner:73: Section [test], line 28: Test failed: Failed to compile shader, hr 0x80004005.
```

Ideally we would be able to specify

```
[require]
shader model >= 2.1
```

[Zebediah Figura (＠zfigura)]

> Ideally we would be able to specify
> [require]
> shader model >= 2.1

That should be simple enough to add :-)

[Giovanni Mascellani (＠giomasce)]

Do you already have implementations for the coarse and fine derivatives? They should rather simple to add. If you can add them to the MR we can actually check that the test values for coarse and fine derivatives are accepted on different devices, to minimize the probability we have to edit them again in the futures.