Sorting a lot of indepent small arrays. #3533

const uniform float MinAlpha = 1e-5f;

struct Box
{
    int xmin, xmax, ymin, ymax;
};

struct Range
{
    int xStart, xEnd;
    int y;
};

struct Row
{
    float* r;
    float* g;
    float* b;
    float* a;
}

struct DeepPixel
{
   uint sampleCount;
   const float* data;
};

struct PixelLayout
{
    int rIdx;
    int gIdx;
    int bIdx;
    int aIdx;
    int zIdx;
    int zBackIdx;
    uint channelCount;
};

bool almostEqual(const float a, const float b, const uniform float epsilon = MinAlpha)
{
    return abs(a - b) < epsilon;
}

inline float getPixelValue( const uniform PixelLayout& layout, const DeepPixel& p, int sampNo, int channel)
{
    return *(p.data + (sampNo * layout.channelCount) + channel);
}

inline float<4> Over(const float<4>& currentV, const float<4>& newV, const float currentTA)
{
    return currentV + (currentTA * newV);
}

void insert(float arr[], const float newVal, const uint n, uint &unique)
{
    unique = n;
    for (uint i = n-1;i>=0;--i)
    {
        const float currentVal = arr[i];
        if (currentVal == newVal) // mixed
        {
            // Value already exists, do not insert
            return;
        }
        if (currentVal > newVal)
        {
            arr[i + 1] = currentVal; // Shift elements to the right
        }
        else
        {
            arr[i + 1] = newVal; // Insert new value
            unique++; // Update unique count
            return;
        }
    }
}

inline float<4> ComputePixel(const DeepPixel& p, const uniform PixelLayout& layout)
{
    float <4> flatResult = {0, 0, 0, 0};

    cif (p.sampleCount == 0)
    {
        return flatResult; // No samples, return empty pixel
    }

    cif (p.sampleCount > 200)
    {
        print("Warning: Sample count exceeds 200, need more Memory.\n");
        return flatResult; // No samples, return empty pixel
    }

    float segs[400];
    uint uniqueCount = 0;
    {
        segs[0] = getPixelValue(layout, p, 0, layout.zIdx); // Start with the first sample's z value
        uniqueCount = 1;
        const float v = getPixelValue(layout, p, 0, layout.zBackIdx);
        insert(segs, v, uniqueCount, uniqueCount);
    }

    for (int i = 1; i < p.sampleCount; ++i)
    {
        const float z = getPixelValue(layout, p, i, layout.zIdx);
        const float zBack = getPixelValue(layout, p, i, layout.zBackIdx);
        insert(segs, z, uniqueCount, uniqueCount);
        if (zBack > z)
        {
            insert(segs, zBack, uniqueCount, uniqueCount);
        }
    }

    segs[uniqueCount] = 1e10f; // Sentinel value for end of array

    // add flatResultAlgo

    return flatResult;
}

export void FlattenKernel(const uniform float* uniform pixelData[], uniform const uint numSamples[], const uniform PixelLayout& layout, const uniform Range& r, uniform Row& row)
{
    foreach(x=r.xStart ... r.xEnd)
    {
        DeepPixel pixel;
        pixel.sampleCount = numSamples[x];
        pixel.data = pixelData[x];
        float<4> color = ComputePixel(pixel, layout);

        row.r[x] = color.x;
        row.g[x] = color.y;
        row.b[x] = color.z;
        row.a[x] = color.w;
    }
}

/home/clusty/CLionProjects/ISPC-CMake-Example-master/simple.ispc:73:34: Performance Warning: Gather required to load value. 
        const float currentVal = arr[i];
                                 ^^^^^^

/home/clusty/CLionProjects/ISPC-CMake-Example-master/simple.ispc:81:13: Performance Warning: Scatter required to store value. 
            arr[i + 1] = currentVal; // Shift elements to the right
            ^^^^^^^^^^

/home/clusty/CLionProjects/ISPC-CMake-Example-master/simple.ispc:85:13: Performance Warning: Scatter required to store value. 
            arr[i + 1] = newVal; // Insert new value
            ^^^^^^^^^^

/home/clusty/CLionProjects/ISPC-CMake-Example-master/simple.ispc:60:12: Performance Warning: Gather required to load value. 
    return *(p.data + (sampNo * layout.channelCount) + channel);
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

/home/clusty/CLionProjects/ISPC-CMake-Example-master/simple.ispc:127:5: Performance Warning: Scatter required to store value. 
    segs[uniqueCount] = 1e10f; // Sentinel value for end of array