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eigen-half.h
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eigen-half.h
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/*
* This implementation is extracted from Eigen:
* Repo: bitbucket.org/eigen/eigen
* File: Eigen/src/Core/arch/CUDA/Half.h
* Commit ID: 96e0f73a35de54f675d825bef5339b2f08e77eb4
*
* Removed a lot of redundant and cuda-specific code.
*/
#define EIGEN_STRONG_INLINE static inline
#define EIGEN_DEVICE_FUNC
// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
//
// The conversion routines are Copyright (c) Fabian Giesen, 2016.
// The original license follows:
//
// Copyright (c) Fabian Giesen, 2016
// All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted.
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// “AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// Standard 16-bit float type, mostly useful for GPUs. Defines a new
// type Eigen::half (inheriting from CUDA's __half struct) with
// operator overloads such that it behaves basically as an arithmetic
// type. It will be quite slow on CPUs (so it is recommended to stay
// in fp32 for CPUs, except for simple parameter conversions, I/O
// to disk and the likes), but fast on GPUs.
#ifndef EIGEN_HALF_CUDA_H
#define EIGEN_HALF_CUDA_H
namespace Eigen {
namespace half_impl {
// Make our own __half definition that is similar to CUDA's.
struct __half {
EIGEN_DEVICE_FUNC __half() : x(0) {}
explicit EIGEN_DEVICE_FUNC __half(unsigned short raw) : x(raw) {}
unsigned short x;
};
EIGEN_STRONG_INLINE EIGEN_DEVICE_FUNC __half raw_uint16_to_half(unsigned short x);
EIGEN_STRONG_INLINE EIGEN_DEVICE_FUNC __half float_to_half_rtne(float ff);
EIGEN_STRONG_INLINE EIGEN_DEVICE_FUNC float half_to_float(__half h);
// Conversion routines, including fallbacks for the host or older CUDA.
// Note that newer Intel CPUs (Haswell or newer) have vectorized versions of
// these in hardware. If we need more performance on older/other CPUs, they are
// also possible to vectorize directly.
EIGEN_STRONG_INLINE EIGEN_DEVICE_FUNC __half raw_uint16_to_half(unsigned short x) {
__half h;
h.x = x;
return h;
}
union FP32 {
unsigned int u;
float f;
};
EIGEN_STRONG_INLINE EIGEN_DEVICE_FUNC __half float_to_half_rtne(float ff) {
#if defined(EIGEN_HAS_CUDA_FP16) && defined(__CUDA_ARCH__) && __CUDA_ARCH__ >= 300
return __float2half(ff);
#elif defined(EIGEN_HAS_FP16_C)
__half h;
h.x = _cvtss_sh(ff, 0);
return h;
#else
FP32 f; f.f = ff;
const FP32 f32infty = { 255 << 23 };
const FP32 f16max = { (127 + 16) << 23 };
const FP32 denorm_magic = { ((127 - 15) + (23 - 10) + 1) << 23 };
unsigned int sign_mask = 0x80000000u;
__half o;
o.x = static_cast<unsigned short>(0x0u);
unsigned int sign = f.u & sign_mask;
f.u ^= sign;
// NOTE all the integer compares in this function can be safely
// compiled into signed compares since all operands are below
// 0x80000000. Important if you want fast straight SSE2 code
// (since there's no unsigned PCMPGTD).
if (f.u >= f16max.u) { // result is Inf or NaN (all exponent bits set)
o.x = (f.u > f32infty.u) ? 0x7e00 : 0x7c00; // NaN->qNaN and Inf->Inf
} else { // (De)normalized number or zero
if (f.u < (113 << 23)) { // resulting FP16 is subnormal or zero
// use a magic value to align our 10 mantissa bits at the bottom of
// the float. as long as FP addition is round-to-nearest-even this
// just works.
f.f += denorm_magic.f;
// and one integer subtract of the bias later, we have our final float!
o.x = static_cast<unsigned short>(f.u - denorm_magic.u);
} else {
unsigned int mant_odd = (f.u >> 13) & 1; // resulting mantissa is odd
// update exponent, rounding bias part 1
f.u += ((unsigned int)(15 - 127) << 23) + 0xfff;
// rounding bias part 2
f.u += mant_odd;
// take the bits!
o.x = static_cast<unsigned short>(f.u >> 13);
}
}
o.x |= static_cast<unsigned short>(sign >> 16);
return o;
#endif
}
EIGEN_STRONG_INLINE EIGEN_DEVICE_FUNC float half_to_float(__half h) {
#if defined(EIGEN_HAS_CUDA_FP16) && defined(__CUDA_ARCH__) && __CUDA_ARCH__ >= 300
return __half2float(h);
#elif defined(EIGEN_HAS_FP16_C)
return _cvtsh_ss(h.x);
#else
const FP32 magic = { 113 << 23 };
const unsigned int shifted_exp = 0x7c00 << 13; // exponent mask after shift
FP32 o;
o.u = (h.x & 0x7fff) << 13; // exponent/mantissa bits
unsigned int exp = shifted_exp & o.u; // just the exponent
o.u += (127 - 15) << 23; // exponent adjust
// handle exponent special cases
if (exp == shifted_exp) { // Inf/NaN?
o.u += (128 - 16) << 23; // extra exp adjust
} else if (exp == 0) { // Zero/Denormal?
o.u += 1 << 23; // extra exp adjust
o.f -= magic.f; // renormalize
}
o.u |= (h.x & 0x8000) << 16; // sign bit
return o.f;
#endif
}
} // end namespace half_impl
} // end namespace Eigen
#endif // EIGEN_HALF_CUDA_H