Finch/tests/run/vectors.fch
Claude 04f1f94a21
Vectors for kernels: masks and select, shuffles and byte lookup, dot_add, @cpu and cpu_has; --cpu native on Nix
- comparisons of vectors give masks (boolxN): select(m, a, b), m.any/all/count, & | ^ !;
  f32x8(list, i, fill) and v.store_part(list, i) for the end of a list (masked load/store)
- v.shuffle(constant lanes), v.lo(), v.hi(), concat(a, b), table.lookup(indices):
  pshufb / vpshufb on x86 (SSSE3 and up), tbl on ARM64 (checked in the assembly, LLVM 18 and 21)
- acc.dot_add(a, b): i32 lanes gain 4 byte products each, exactly; vpdpbusd with AVX-VNNI or AVX-512 VNNI,
  usdot/sdot/udot on ARM64, the sum written out elsewhere (pmaddwd); run here with all three paths agreeing
- @cpu("avx2,fma") fn: LLVM target-features for one function (+evex512 for AVX-512, which LLVM 18+ needs);
  cpu_has("avx2"): CPUID + XGETBV on x86, hwcaps on Linux ARM64, sysctl on macOS; a wide vector can't be passed
  between functions with different @cpu (its registers differ), and the compiler says so
- the compiler asks clang which features --cpu means (its predefined macros, cached), so dot_add picks the instruction
- Nix's clang wrapper dropped -march=native in nix-shell (reproduced): finch tells it NIX_ENFORCE_NO_NATIVE=0, shell.nix too,
  and warns if --cpu native still made no difference

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Psc42moPLwP43Cmb9oZqSR
2026-11-01 15:41:47 +00:00

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// Vectors: N numbers side by side, worked on all at once (SIMD)
struct Particle {
f32x8 pos
int id = 7
}
fn scale(f32x8 v, f32 k) -> f32x8 {
return v * k
}
// a dot product of two lists, 8 at a time, with the rest one by one
fn dot([]f32 a, []f32 b) -> f32 {
acc := f32x8(0.0)
i := 0
while i + 8 <= a.len {
acc = f32x8(a, i).muladd(f32x8(b, i), acc)
i += 8
}
total := acc.sum()
while i < a.len {
total += a[i] * b[i]
i += 1
}
return total
}
fn main() {
a := f32x4(1.0, 2.0, 3.0, 4.0)
b := f32x4(0.5)
print(a + b, a * 2.0, 10.0 - a, -a)
print(a.sum(), a.min(), a.max(), a.dot(a), a.len)
print((a * a).sqrt(), f32x4(1.5, -1.5, 2.5, -0.2).round(), f32x4(1.7).floor(), f32x4(1.2).ceil())
print(abs(f32x4(-1.0, 2.0, -3.0, 4.0)), min(a, 2.5), max(a, f32x4(2.0)), clamp(a, 1.5, 3.5))
// lanes
a[0] = 9.0
print(a[0], a[3], a)
print((a == f32x4(9.0, 2.0, 3.0, 4.0)).all(), (a != a).any())
// whole numbers, bits, conversions
n := i32x8(1, 2, 3, 4, 5, 6, 7, 8)
print(n * 3 - 1, n << 2, n & 1, ~n, n.sum(), n.max())
print(f32x8(n) / 2.0, i32x8(f32x8(2.9)), i16x8(n), u8x16(200).sum())
print(abs(i32x4(-3, 3, -7, 0)), min(u8x16(5), u8x16(9)).max())
// from lists and back
[]f32 data
for i in 0..20 {
data.push(f32(i))
}
v := f32x8(data, 4)
print(v)
(v * 10.0).store(data, 12)
print(data)
print(dot(data, data))
// in structs, arrays, functions, and str()
p := Particle(pos: f32x8(1.0))
p.pos = scale(p.pos, 3.0)
p.pos[7] = 0.5
print(p)
[]f64x4 list
list.push(f64x4(1.0, 2.0, 3.0, 4.0))
list.push(list[0] * list[0])
print(list, str(list[1]).len)
i64x2 big = i64x2(1 << 40, -5)
print(big + big)
}