Simd Sumby - Lo — ContextQMD

SumBy transforms a collection using an iteratee function and sums the result using SIMD instructions. The automatic dispatch functions (e.g., SumByInt8) will select the best SIMD variant based on CPU capabilities. The specific variants (e.g., SumByInt8x32) use a fixed SIMD instruction set regardless of CPU capabilities.

Note: The automatic dispatch functions (e.g., SumByInt8) will use the best available SIMD variant for the current CPU. Use specific variants (e.g., SumByInt8x32) only if you know your target CPU supports that instruction set.

type Person struct {
    Name string
    Age  int8
}

people := []Person{
    {Name: "Alice", Age: 25},
    {Name: "Bob", Age: 30},
    {Name: "Charlie", Age: 35},
}

// Automatic dispatch - uses best available SIMD
sum := simd.SumByInt8(people, func(p Person) int8 {
    return p.Age
})
// 90

type Product struct {
    Name  string
    Price float32
    Stock int32
}

products := []Product{
    {Name: "Widget", Price: 10.50, Stock: 5},
    {Name: "Gadget", Price: 20.00, Stock: 3},
    {Name: "Tool", Price: 15.75, Stock: 2},
}

// Sum stock value using specific AVX2 variant
sum := simd.SumByFloat32x8(products, func(p Product) float32 {
    return p.Price * float32(p.Stock)
})
// 152.5

type Metric struct {
    Value uint16
}

metrics := []Metric{
    {Value: 100},
    {Value: 200},
    {Value: 300},
    {Value: 400},
}

// Using AVX variant - works on all amd64
sum := simd.SumByUint16x8(metrics, func(m Metric) uint16 {
    return m.Value
})
// 1000

// Empty collection returns 0
type Item struct {
    Count int64
}

sum := simd.SumByInt64([]Item{}, func(i Item) int64 {
    return i.Count
})
// 0