drop float16 dependency

goos: darwin
goarch: arm64
pkg: github.com/ollama/ollama/convert/float16
cpu: Apple M3 Max
BenchmarkFloat16/x448/float16-16                     159           7398462 ns/op
BenchmarkFloat16/simple-16                           512           2327098 ns/op
PASS
ok      github.com/ollama/ollama/convert/float16        2.553s

convert/float16/float16.go

@@ -0,0 +1,97 @@
+package float16
+
+import (
+	"math"
+)
+
+func FromFloat32s(f32s []float32) (u16s []uint16) {
+	u16s = make([]uint16, len(f32s))
+	for i := range f32s {
+		bits := math.Float32bits(f32s[i])
+		sign := (bits >> 31) & 0x1
+		exponent := (bits >> 23) & 0xFF
+		mantissa := bits & 0x7FFFFF
+		if exponent == 0xFF {
+			if mantissa == 0 {
+				// Infinity
+				u16s[i] = uint16((sign << 15) | 0x7C00)
+			} else {
+				// NaN
+				u16s[i] = uint16((sign << 15) | 0x7C00 | (mantissa >> 13))
+			}
+		} else if exponent == 0 && mantissa == 0 {
+			// Zero
+			u16s[i] = uint16(sign << 15)
+		} else {
+			// Convert exponent from FP32 bias (127) to FP16 bias (15)
+			exponent := int(exponent) - 127 + 15
+			if exponent >= 31 {
+				// Overflow to infinity
+				u16s[i] = uint16((sign << 15) | 0x7C00)
+			} else if exponent <= 0 {
+				// Underflow - create subnormal or zero
+				if exponent < -10 {
+					u16s[i] = uint16(sign << 15) // Zero
+				} else {
+					// Subnormal number
+					mantissa = (mantissa | 0x800000) >> uint(-exponent+1)
+					u16s[i] = uint16((sign << 15) | (mantissa >> 13))
+				}
+			} else {
+				// Normal number - truncate mantissa from 23 to 10 bits
+				u16s[i] = uint16((sign << 15) | (uint32(exponent) << 10) | (mantissa >> 13))
+			}
+		}
+	}
+
+	return u16s
+}
+
+func Float32s(u16s []uint16) (f32s []float32) {
+	f32s = make([]float32, len(u16s))
+	for i := range u16s {
+		sign := (u16s[i] >> 15) & 0x1
+		exponent := (u16s[i] >> 10) & 0x1F
+		mantissa := u16s[i] & 0x3FF
+
+		var u32 uint32
+		switch exponent {
+		case 0:
+			if mantissa == 0 {
+				// Zero
+				u32 = uint32(sign) << 31
+			} else {
+				// Subnormal - convert to normal
+				// Find leading 1 bit
+				shift := 0
+				temp := mantissa
+				for temp&0x400 == 0 {
+					temp <<= 1
+					shift++
+				}
+
+				exponent := 127 - 15 + 1 - shift
+				mantissa := (uint32(temp&0x3FF) << 13)
+
+				u32 = (uint32(sign) << 31) | (uint32(exponent) << 23) | mantissa
+			}
+		case 0x1F:
+			if mantissa == 0 {
+				// Infinity
+				u32 = (uint32(sign) << 31) | 0x7F800000
+			} else {
+				// NaN
+				u32 = (uint32(sign) << 31) | 0x7F800000 | (uint32(mantissa) << 13)
+			}
+		default:
+			// Normal number
+			exponent := uint32(exponent) - 15 + 127
+			mantissa := uint32(mantissa) << 13
+
+			u32 = (uint32(sign) << 31) | (exponent << 23) | mantissa
+		}
+
+		f32s[i] = math.Float32frombits(u32)
+	}
+	return f32s
+}

convert/float16/float16_test.go

@@ -0,0 +1,75 @@
+package float16
+
+import (
+	"math"
+	"math/rand/v2"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+)
+
+func TestFloat16(t *testing.T) {
+	cases := []struct {
+		name  string
+		input uint16
+		want  uint32
+	}{
+		// Zero cases
+		{"positive zero", 0x0000, 0x0},
+		{"negative zero", 0x8000, 0x80000000},
+
+		// Normal numbers
+		{"one", 0x3C00, 0x3F800000},
+		{"negative one", 0xBC00, 0xBF800000},
+		{"two", 0x4000, 0x40000000},
+		{"half", 0x3800, 0x3F000000},
+		{"max normal", 0x7BFF, 0x477fe000},
+		{"min positive normal", 0x0400, 0x38800000},
+
+		// Infinity cases
+		{"positive infinity", 0x7C00, 0x7F800000},
+		{"negative infinity", 0xFC00, 0xFF800000},
+
+		// NaN cases
+		{"NaN", 0x7C01, 0x7f802000},
+		{"NaN with payload", 0x7E00, 0x7FC00000},
+
+		// Subnormal cases
+		{"min positive subnormal", 0x0001, 0x33800000},
+		{"max subnormal", 0x03FF, 0x387fc000},
+
+		// Common values
+		{"pi approximation", 0x4248, 0x40490000},
+		{"e approximation", 0x416F, 0x402de000},
+	}
+
+	for _, tt := range cases {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			t.Run("Float32s", func(t *testing.T) {
+				got := Float32s([]uint16{tt.input})[0]
+				if diff := cmp.Diff(tt.want, math.Float32bits(got)); diff != "" {
+					t.Errorf("Float32s mismatch (-want +got):\n%s", diff)
+				}
+			})
+
+			t.Run("FromFloat32s", func(t *testing.T) {
+				got := FromFloat32s([]float32{math.Float32frombits(tt.want)})
+				if diff := cmp.Diff([]uint16{tt.input}, got); diff != "" {
+					t.Errorf("FromFloat32s mismatch (-want +got):\n%s", diff)
+				}
+			})
+		})
+	}
+}
+
+func BenchmarkFloat16(b *testing.B) {
+	f32s := make([]float32, 1_000_000)
+	for i := range f32s {
+		f32s[i] = rand.Float32()
+	}
+	for b.Loop() {
+		Float32s(FromFloat32s(f32s))
+	}
+}