Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

mix: reimplement based on std::lerp reference implementation. #219

Open
wants to merge 1 commit into
base: main
Choose a base branch
from
Open

mix: reimplement based on std::lerp reference implementation. #219

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Jump to
Jump to file
Failed to load files.
Diff view
Diff view
31 changes: 29 additions & 2 deletions modules/compiler/builtins/abacus/generate/abacus_detail_common/abacus_detail_common.in
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -115,8 +115,35 @@ template<typename T> T degrees(const T& t) {
return t * T(57.295779513082320876798154814105170332405472466564321);
}

template<typename T, typename U> T mix(const T& x, const T& y, const U& a) {
return x + ((y - x) * T(a));
template <typename T>
T mix(const T &a, const T &b, const T &t) {
// Unoptimized vector version of the implementation of std::lerp given in
// https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p0811r3.html
// adjusted to support non-finite arguments.
//
// Unlike std::lerp, OpenCL mix returns an undefined result if
// !(t >= 0 && t <= 1), so we could simplify slightly, but we aim to behave
// sensibly for this.

using SignedType = typename TypeTraits<T>::SignedType;

// The direct translation of the expression mix/lerp is defined as. This
// version is used in most cases, but has issues around t=1 and does not
// account for the possibility b-a overflows.
const T x = a + t * (b - a);

// Correct for the issues around t=1 by returning b in edge cases.
const SignedType useb =
__abacus_select(b <= x, x <= b, (t > T(1)) == (b > a)) |
((t == T(1)) & (x == x));

// Alternative definition that avoids overflow of b-a. This version is used
// when a and b are finite numbers with different signs.
const T y = t * b + (T(1) - t) * a;
const SignedType usey = isfinite(a) & isfinite(b) &
(((a <= 0) & (b >= 0)) | ((a >= 0) & (b <= 0)));

return __abacus_select(__abacus_select(x, b, useb), y, usey);
}

template<typename T> T radians(const T& t) {
Expand Down
6 changes: 3 additions & 3 deletions modules/compiler/builtins/abacus/source/abacus_common/mix.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -21,9 +21,9 @@
TYPE __abacus_mix(TYPE x, TYPE y, TYPE a) { \
return abacus::detail::common::mix(x, y, a); \
}
#define DEF2(TYPE, TYPE2) \
TYPE __abacus_mix(TYPE x, TYPE y, TYPE2 a) { \
return abacus::detail::common::mix(x, y, a); \
#define DEF2(TYPE, TYPE2) \
TYPE __abacus_mix(TYPE x, TYPE y, TYPE2 a) { \
return abacus::detail::common::mix<TYPE>(x, y, a); \
}

#ifdef __CA_BUILTINS_HALF_SUPPORT
Expand Down
37 changes: 6 additions & 31 deletions source/cl/test/UnitCL/source/ktst_precision.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1633,24 +1633,12 @@ TEST_P(HalfMathBuiltins, Precision_53_Half_mix) {
GTEST_SKIP();
}

// TODO: CA-2882: Vector widths 2 and 4 don't work
#ifdef __arm__
if ((getParam() == 2) || (getParam() == 4)) {
GTEST_SKIP();
}
#endif

auto mix_ref = [](cl_float x, cl_float y, cl_float a) -> cl_float {
// Our reference for mix is inaccurate due to intermediate rounding, even if
// we use float rather than half, but because we test with MAX_ULP_ERROR,
// this does not matter for the overall test.
cl_float sub = y - x;

// Check for overflow and underflow of intermediate
const cl_half sub_as_half = ConvertFloatToHalf(sub);
if (IsInf(sub_as_half)) {
sub = std::copysign(INFINITY, sub);
} else if (0 == (sub_as_half & ~TypeInfo<cl_half>::sign_bit)) {
sub = std::copysign(0.0f, sub);
}

return x + sub * a;
};

Expand All @@ -1666,25 +1654,12 @@ TEST_P(HalfMathBuiltins, Precision_53_Half_mix_scalar) {
GTEST_SKIP();
}

// TODO: CA-2731: Vector widths 2 and 8 don't work
// TODO: CA-2882: Vector width 4 doesn't work
#ifdef __arm__
if ((getParam() == 2) || (getParam() == 4) || (getParam() == 8)) {
GTEST_SKIP();
}
#endif

auto mix_ref = [](cl_float x, cl_float y, cl_float a) -> cl_float {
// Our reference for mix is inaccurate due to intermediate rounding, even if
// we use float rather than half, but because we test with MAX_ULP_ERROR,
// this does not matter for the overall test.
cl_float sub = y - x;

// Check for overflow and underflow of intermediate
const cl_half sub_as_half = ConvertFloatToHalf(sub);
if (IsInf(sub_as_half)) {
sub = std::copysign(INFINITY, sub);
} else if (0 == (sub_as_half & ~TypeInfo<cl_half>::sign_bit)) {
sub = std::copysign(0.0f, sub);
}

return x + sub * a;
};

Expand Down