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drawElements Quality Program Test Specification
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Copyright 2014 The Android Open Source Project

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

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distributed under the License is distributed on an "AS IS" BASIS,
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    Shader compiler performance tests

Tests:
 + dEQP-GLES2.performance.compiler.*

Includes:
 + Shader compile, link and specialization (draw call -time) time measurements
 + Tests for impact of cache hits on compilation time (note: in release 2012.4)
 + Front-end time estimation with invalid shaders
 + Typical use cases
   - Vertex and fragment lighting
   - Mandelbrot viewer
   - Normal mapping, parallax and relief mapping (note: in release 2012.4)
 + Synthetic cases
   - A number of texture lookups blended together in fragment shader
   - Single or nested loops
   - Single expression consisting of a variable number of vec4 multiplications
 + Shaders designed to stress compiler (note: in release 2012.4)
   - High register pressure
   - Lots of control flow

Excludes:
 + Shader functional testing

Description:

Shader compiler performance tests measure the time to compile GLSL shader programs.
The tests will take into account implementations that postpone final compilation
until execution of a draw call.

Separate cases are made for testing compilation time when avoiding cache hits and
when allowing them (note that tests that allow cache will be in release 2012.4).
Cache-avoiding cases use a different shader for different iterations of the same
test case, whereas cache-allowing cases use the same shader for all iterations.
Cache hits are however only ever allowed between the iterations of a case and not
across separate cases.

The method for defeating the shader cache is to append a postfix to all uniform,
attribute and varying names. The postfix depends on the current time as well as
the case that is in question. In case of cache-avoiding cases, the postfix also
depends on the current iteration. This method forces at least re-linking.

Front-end time is estimated by compiling invalid shaders with either an invalid
character at the end of the shader or an invalid statement at the end of the main()
block.

The result value is the average number of milliseconds used per test case
iteration. In cases that allow cache hits the average excludes the first
compilation.

Before any measurements are done, each test case first draws with a simple dummy
shader for warm-up.

Overview for valid shader cases:
 - 1. Create program and shaders; compile and link
 - 2. Set inputs and draw a small quad
 - 3. Flush
 - 4. Repeat without step 1
 - 5. Compute difference of times measured for 1-3 and 4 and record it as
      compilation time
 - Repeat the above steps several times and compute average

Overview for invalid shader cases (front-end time estimation):
 - 1. Create program and invalid shaders; compile (expect failure)
 - 2. Record time measured for step 1
 - Repeat the above steps several times and compute average