volk_32f_invsqrt_32f.h

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/* -*- c++ -*- */
/*
 * Copyright 2013, 2014 Free Software Foundation, Inc.
 *
 * This file is part of VOLK
 *
 * SPDX-License-Identifier: LGPL-3.0-or-later
 */
 
#ifndef INCLUDED_volk_32f_invsqrt_32f_a_H
#define INCLUDED_volk_32f_invsqrt_32f_a_H
 
#include <inttypes.h>
#include <math.h>
#include <stdio.h>
#include <string.h>
 
static inline float Q_rsqrt(float number)
{
    float x2;
    const float threehalfs = 1.5F;
    union f32_to_i32 {
        int32_t i;
        float f;
    } u;
 
    x2 = number * 0.5F;
    u.f = number;
    u.i = 0x5f3759df - (u.i >> 1);               // what the fuck?
    u.f = u.f * (threehalfs - (x2 * u.f * u.f)); // 1st iteration
    // u.f  = u.f * ( threehalfs - ( x2 * u.f * u.f ) );   // 2nd iteration, this can be
    // removed
 
    return u.f;
}
 
#ifdef LV_HAVE_AVX
#include <immintrin.h>
 
static inline void
volk_32f_invsqrt_32f_a_avx(float* cVector, const float* aVector, unsigned int num_points)
{
    unsigned int number = 0;
    const unsigned int eighthPoints = num_points / 8;
 
    float* cPtr = cVector;
    const float* aPtr = aVector;
    __m256 aVal, cVal;
    for (; number < eighthPoints; number++) {
        aVal = _mm256_load_ps(aPtr);
        cVal = _mm256_rsqrt_ps(aVal);
        _mm256_store_ps(cPtr, cVal);
        aPtr += 8;
        cPtr += 8;
    }
 
    number = eighthPoints * 8;
    for (; number < num_points; number++)
        *cPtr++ = Q_rsqrt(*aPtr++);
}
#endif /* LV_HAVE_AVX */
 
 
#ifdef LV_HAVE_SSE
#include <xmmintrin.h>
 
static inline void
volk_32f_invsqrt_32f_a_sse(float* cVector, const float* aVector, unsigned int num_points)
{
    unsigned int number = 0;
    const unsigned int quarterPoints = num_points / 4;
 
    float* cPtr = cVector;
    const float* aPtr = aVector;
 
    __m128 aVal, cVal;
    for (; number < quarterPoints; number++) {
 
        aVal = _mm_load_ps(aPtr);
 
        cVal = _mm_rsqrt_ps(aVal);
 
        _mm_store_ps(cPtr, cVal); // Store the results back into the C container
 
        aPtr += 4;
        cPtr += 4;
    }
 
    number = quarterPoints * 4;
    for (; number < num_points; number++) {
        *cPtr++ = Q_rsqrt(*aPtr++);
    }
}
#endif /* LV_HAVE_SSE */
 
 
#ifdef LV_HAVE_NEON
#include <arm_neon.h>
 
static inline void
volk_32f_invsqrt_32f_neon(float* cVector, const float* aVector, unsigned int num_points)
{
    unsigned int number;
    const unsigned int quarter_points = num_points / 4;
 
    float* cPtr = cVector;
    const float* aPtr = aVector;
    float32x4_t a_val, c_val;
    for (number = 0; number < quarter_points; ++number) {
        a_val = vld1q_f32(aPtr);
        c_val = vrsqrteq_f32(a_val);
        vst1q_f32(cPtr, c_val);
        aPtr += 4;
        cPtr += 4;
    }
 
    for (number = quarter_points * 4; number < num_points; number++)
        *cPtr++ = Q_rsqrt(*aPtr++);
}
#endif /* LV_HAVE_NEON */
 
 
#ifdef LV_HAVE_GENERIC
 
static inline void volk_32f_invsqrt_32f_generic(float* cVector,
                                                const float* aVector,
                                                unsigned int num_points)
{
    float* cPtr = cVector;
    const float* aPtr = aVector;
    unsigned int number = 0;
    for (number = 0; number < num_points; number++) {
        *cPtr++ = Q_rsqrt(*aPtr++);
    }
}
#endif /* LV_HAVE_GENERIC */
 
#ifdef LV_HAVE_AVX
#include <immintrin.h>
 
static inline void
volk_32f_invsqrt_32f_u_avx(float* cVector, const float* aVector, unsigned int num_points)
{
    unsigned int number = 0;
    const unsigned int eighthPoints = num_points / 8;
 
    float* cPtr = cVector;
    const float* aPtr = aVector;
    __m256 aVal, cVal;
    for (; number < eighthPoints; number++) {
        aVal = _mm256_loadu_ps(aPtr);
        cVal = _mm256_rsqrt_ps(aVal);
        _mm256_storeu_ps(cPtr, cVal);
        aPtr += 8;
        cPtr += 8;
    }
 
    number = eighthPoints * 8;
    for (; number < num_points; number++)
        *cPtr++ = Q_rsqrt(*aPtr++);
}
#endif /* LV_HAVE_AVX */
 
#endif /* INCLUDED_volk_32f_invsqrt_32f_a_H */