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1-------------------------------------------------------------------------
2drawElements Quality Program Test Specification
3-----------------------------------------------
4
5Copyright 2014 The Android Open Source Project
6
7Licensed under the Apache License, Version 2.0 (the "License");
8you may not use this file except in compliance with the License.
9You may obtain a copy of the License at
10
11     http://www.apache.org/licenses/LICENSE-2.0
12
13Unless required by applicable law or agreed to in writing, software
14distributed under the License is distributed on an "AS IS" BASIS,
15WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16See the License for the specific language governing permissions and
17limitations under the License.
18-------------------------------------------------------------------------
19    Performance tests
20
21This test specification describes general techniques and methodologies used
22in performance test cases.
23
24
25Measuring performance:
26
27Performance test cases must satisfy following conditions:
28
29 + Result should represent the performance of the tested feature or use case.
30   - Use of any other features should be kept at minimum.
31   - Architecture-specific optimizations should not affect result unless they
32     target the feature being tested.
33   - Measurement overhead should be minimized.
34
35 + Hardware must be utilized to the maximum.
36   - In most cases total throughput is more important than latency.
37   - Latency is measured where it matters.
38   - Test cases should behave like other graphics-intensive applications on
39     that platform. This usually means that test cases should render multiple
40	 frames and utilize platform-defined standard mechanisms to display each
41	 frame on screen.
42
43 + Test result should be stable across test runs.
44   - Final result should be a function of results from multiple iterations if
45     performance is expected to vary between iterations (due to undeterministic
46     scheduling for example).
47   - Simple average may not always be the right function, often stability of
48     the performance is more important from user experience perspective.
49
50 + Test result values should be meaningful.
51   - Result should be meaningful without knowing the exact implementation
52     details of the test case.
53   - Good example: Millions of pixels or vertices with shader X per second
54   - Bad example: Frames per second
55
56 + Results can be compared across different implementations and configurations.
57   - If possible, configuration changes (viewport size for example) should not
58	 affect the test result.
59   - Where configuration may affect the result, test log should include the
60	 configuration details.
61
62
63Test output:
64
65Test cases will log at least following variables, if available:
66
67 * Viewport size
68 * Color, depth, stencil and multisample bits
69 * Number of draw calls
70 * Shader program source
71 * Automatic calibration values
72 * Individual iteration times (if iteration count is reasonable)
73 * Minimum and maximum iteration times
74 * Average iteration time
75 * Minimum and maximum computed performance
76 * Average computed performance
77
78
79Shader execution tests:
80
81Shader execution tests measure the performance of single pair of vertex and
82fragment shaders, optionally combined with fixed-function per-fragment
83operations such as blending.
84
85Each iteration (frame) renders N grids of quads. Each grid, drawn with single
86draw call, fills the screen entirely without any overlap between quads.
87The number of quads depends on targeted vertex load. Test cases targeting
88fragment shaders only use a single quad. N (number of times screen is filled)
89is chosen either automatically to target certain iteration time or specified
90by the test case explicitly.
91
92Test cases that measure fragment-side performance must make sure fragments
93are not discarded early due to Z-culling or any other optimization. The
94preferred way to do this is to enable simple additive blending. The extra
95cost of that is one read from the framebuffer and per-channel saturating
96additions.
97
98The result is MPix/s, MVert/s or weighted sum of both depending on test
99case type.
100