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// softclip
// Copyright (C) 2008, 2009 Tim Blechmann
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; see the file COPYING. If not, write to
// the Free Software Foundation, Inc., 51 Franklin Street - Fifth Floor,
// Boston, MA 02110-1301, USA.
#ifndef SIMD_SOFTCLIP_HPP
#define SIMD_SOFTCLIP_HPP
#include <cassert>
#include <cmath>
#include "vec.hpp"
#include "detail/define_macros.hpp"
#if defined(__GNUC__) && defined(NDEBUG)
#define always_inline inline __attribute__((always_inline))
#else
#define always_inline inline
#endif
namespace nova {
namespace detail {
struct softclip
{
template <typename FloatType>
static FloatType s_run(FloatType arg)
{
FloatType abs = std::fabs(arg);
if (abs < FloatType(0.5))
return arg;
else
return (abs - FloatType(0.25)) / arg;
}
template <typename FloatType>
always_inline FloatType operator()(FloatType arg) const
{
return s_run(arg);
}
#if defined(__SSE__) || defined(__AVX__)
/* this computes both parts of the branch
*
* benchmarks (core2) showed:
* 6.5 seconds for simdfied code
* 5.3 seconds for non-simd code for samples with abs(sample) < 0.5
* 17 seconds when 50% of the samples have abs(sample) < 0.5
* 26 seconds for samples with abs(sample) > 0.5
*
* on intel nethalem cpus, the simdfied code is faster than all non-simd code
* */
template <typename FloatType>
always_inline vec<FloatType> operator()(vec<FloatType> arg) const
{
typedef vec<FloatType> vec_type;
const vec_type const05 = vec_type::gen_05();
const vec_type const025 (0.25);
vec_type abs_ = abs(arg);
vec_type selecter = mask_lt(abs_, const05);
vec_type alt_ret = (abs_ - const025) / arg;
return select(alt_ret, arg, selecter);
}
#else
template <typename FloatType>
always_inline vec<FloatType> operator()(vec<FloatType> arg) const
{
return arg.collect(softclip::s_run<FloatType>);
}
#endif
};
} /* namespace detail */
NOVA_SIMD_DEFINE_UNARY_WRAPPER(softclip, detail::softclip)
} /* namespace nova */
#undef always_inline
#endif /* SIMD_SOFTCLIP_HPP */
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