sobolbn.h

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// SPDX-License-Identifier: Apache-2.0
// Copyright Contributors to the OpenQMC Project.
 
 
#pragma once
 
#include "bntables.h"
#include "gpu.h"
#include "owen.h"
#include "pcg.h"
#include "sampler.h"
#include "state.h"
 
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <cstring>
 
namespace oqmc
{
 
class SobolBnImpl
{
    // See SamplerInterface for public API documentation.
    friend SamplerInterface<SobolBnImpl>;
 
    struct CacheType
    {
        std::uint32_t keyTable[bntables::size];
        std::uint32_t rankTable[bntables::size];
    };
 
    static constexpr std::size_t cacheSize = sizeof(CacheType);
    static void initialiseCache(void* cache);
 
    /*AUTO_DEFINED*/ SobolBnImpl() = default;
    OQMC_HOST_DEVICE SobolBnImpl(State64Bit state, const CacheType* cache);
    OQMC_HOST_DEVICE SobolBnImpl(int x, int y, int frame, int index,
                                 const void* cache);
 
    OQMC_HOST_DEVICE SobolBnImpl newDomain(int key) const;
    OQMC_HOST_DEVICE SobolBnImpl newDomainSplit(int key, int size,
                                                int index) const;
    OQMC_HOST_DEVICE SobolBnImpl newDomainDistrib(int key, int index) const;
 
    template <int Size>
    OQMC_HOST_DEVICE void drawSample(std::uint32_t sample[Size]) const;
 
    template <int Size>
    OQMC_HOST_DEVICE void drawRnd(std::uint32_t rnd[Size]) const;
 
    State64Bit state;
    const CacheType* cache;
};
 
inline void SobolBnImpl::initialiseCache(void* cache)
{
    assert(cache);
 
    auto typedCache = static_cast<CacheType*>(cache);
 
    std::memcpy(typedCache->keyTable, bntables::sobol::keyTable,
                sizeof(bntables::sobol::keyTable));
    std::memcpy(typedCache->rankTable, bntables::sobol::rankTable,
                sizeof(bntables::sobol::rankTable));
}
 
inline SobolBnImpl::SobolBnImpl(State64Bit state, const CacheType* cache)
    : state(state), cache(cache)
{
    assert(cache);
}
 
inline SobolBnImpl::SobolBnImpl(int x, int y, int frame, int index,
                                const void* cache)
    : state(x, y, frame, index), cache(static_cast<const CacheType*>(cache))
{
    assert(cache);
}
 
inline SobolBnImpl SobolBnImpl::newDomain(int key) const
{
    return {state.newDomain(key), cache};
}
 
inline SobolBnImpl SobolBnImpl::newDomainSplit(int key, int size,
                                               int index) const
{
    return {state.newDomainSplit(key, size, index), cache};
}
 
inline SobolBnImpl SobolBnImpl::newDomainDistrib(int key, int index) const
{
    return {state.newDomainDistrib(key, index), cache};
}
 
template <int Size>
void SobolBnImpl::drawSample(std::uint32_t sample[Size]) const
{
    constexpr auto xBits = State64Bit::spatialEncodeBitSizeX;
    constexpr auto yBits = State64Bit::spatialEncodeBitSizeY;
 
    static_assert(xBits == bntables::xBits,
                  "Pixel x encoding must match table.");
    static_assert(yBits == bntables::yBits,
                  "Pixel y encoding must match table.");
 
    const auto table = bntables::tableValue<xBits, yBits, 0>(
        state.pixelId, pcg::output(state.patternId), cache->keyTable,
        cache->rankTable);
 
    shuffledScrambledSobol<Size>(state.sampleId ^ table.rank, table.key,
                                 sample);
}
 
template <int Size>
void SobolBnImpl::drawRnd(std::uint32_t rnd[Size]) const
{
    state.newDomain(state.pixelId).drawRnd<Size>(rnd);
}
 
using SobolBnSampler = SamplerInterface<SobolBnImpl>;
 
} // namespace oqmc