This series upgrades the ARB_shader_precision test generator with
support for complex function tolerances.
The ARB_shader_precision spec does not give specific guidance in regard
to acceptable error ranges for complex functions, supplying only the
murky "Built-in functions defined in the specification with an equation
built from the above operations inherit the above errors." Currently,
the shader_precision tests allow zero tolerance for complex functions,
but this is causing many false negatives and needs to be improved.
This series is my best attempt at due diligence - any discussion/input
is certainly welcomed
The theory behind this is probably worth a blog post and I won't belabor
the point here, but this series basically implements a filter for the
test_suite dict that will drop any test vectors that would push a
function's output into regions of greatly multiplied error - the
"badlands". If the output does not trespass on the badlands, then the
error estimate in ulps is calculated and attached to the current test
vector for the shader_test to use as the allowable error range when
analyzing the output generated on the GPU during test run-time.
The bigfloat package is a necessary dependency for this filter, as it
provides both arbitrary-size floating point operations and it allows all
floating point values and operations in a code block to be forced into a
particular precision, leaving no question as to what precision was
employed for an intermediate calculation. This comes in handy when
running the reference versions of the complex built-ins. Performance
impact is small (~6s for the entire gen_shader_precision_tests.py script
on IvyBridge i7 @ 2.9GHz) and is localized to build-time.
The technique described above actually takes very little python code to
construct - most of the complexity is in dealing with the polymorphic
nature of the GLSL built-ins - componentwise vs. non-componentwise
parameters, etc.
Micah Fedke (3):
arb_shader_precision: support scalar values in shader_runner_format
arb_shader_precision: add framework for calculating tolerances for
complex functions
arb_shader_precision: enable calculation of complex function tolerances
CMakeLists.txt | 1 +
cmake/Modules/FindPythonBigfloat.cmake | 43
+++++++++
generated_tests/gen_shader_precision_tests.py | 650
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++------
generated_tests/templates/gen_shader_precision_tests/fs.mako | 51
++++++----
generated_tests/templates/gen_shader_precision_tests/gs.mako | 51
++++++----
generated_tests/templates/gen_shader_precision_tests/vs.mako | 51
++++++----
6 files changed, 765 insertions(+), 82 deletions(-)
Changes since original:
Review comments addressed
- explicitly cast literals to BigFloats
- updated high_precision and low_precision for more clarity (use native
precisions)
- removed _floatToBits and _bitsToFloat as they are no longer used
- clarified _ulpsize return
- renamed _sanitize_arg to _listify
- renamed _to_bigfloat_list to _to_bigfloat
- added an assert to _to_bigfloat to ensure proper types are passed in,
and replaced double-map with list generator in return value
- commented all reference function with descriptions, inputs and outputs
- replaced non-componentwise arg array generation for loop with a map
Public repo:
http://cgit.collabora.com/git/user/fedke.m/piglit.git/log/?h=complex_tolerances_v3
--
Micah Fedke
Collabora Ltd.
+44 1223 362967
https://www.collabora.com/
https://twitter.com/collaboraltd
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