wave_sum

wave_sum :: (T x) -> T {...}

pipeline AverageLuminance {
  pass "Main" {
    compute "Main" [64, 1, 1] {
    uint localIdx = input.local_index;

    // Sample luminance at this thread's location
    float luminance = computeLuminance(input.global_id);

    // Sum luminance across all threads in the wave
    float waveTotal = wave_sum(luminance);

    // Calculate average (assuming 32-lane wave)
    float waveAvg = waveTotal / 32.0;

    // Use the result on one invocation
    if (localIdx == 0u) {
        float _ = waveAvg;
    }
    }
  }
}

// Sum values across wave for reduction
float localSum = computeValue(input.local_index);
float waveSum = wave_sum(localSum);

// Compute average across wave
float value = sample(tex, uv).r;
float sum = wave_sum(value);
float average = sum / float(waveSize);

// Count how many lanes have a value in range
float inRange = (value >= min && value < max) ? 1.0 : 0.0;
float count = wave_sum(inRange);

// Wave-level sum is part of prefix sum algorithm
float local = data[input.local_index];
float waveTotal = wave_sum(local);

// Gather statistics across wave
float luminance = getLuminance(color);
float totalLum = wave_sum(luminance);

// Requires GL_KHR_shader_subgroup_arithmetic
subgroupAdd(x)

WaveActiveSum(x)