Runner for Ollama engine

This provides integration with the new Ollama engine
(5824541 next ollama runner (#7913)) and the rest of the Ollama
infrastructure such as the runner and Ollama server.

In addition, it also builds out the KV cache infrastructure to
support requirements of how Ollama runs models such as:
 - Parallel processing
 - Memory management for defragmentation and shifting
 - Multi-modal modals

Both old and new engines continue to be supported. By default, only
the old engine is used. To enable the new engine:

Start the server with the OLLAMA_NEW_ENGINE environment variable set:
OLLAMA_NEW_ENGINE=1 ./ollama serve

Start a model that is supported by the Ollama engine. This one is Llama 3.1 8b Q4_K_M:
./ollama run jessegross/llama3.1

runner/common/stop.go

@@ -0,0 +1,96 @@
+package common
+
+import (
+	"strings"
+)
+
+func FindStop(sequence string, stops []string) (bool, string) {
+	for _, stop := range stops {
+		if strings.Contains(sequence, stop) {
+			return true, stop
+		}
+	}
+
+	return false, ""
+}
+
+func ContainsStopSuffix(sequence string, stops []string) bool {
+	for _, stop := range stops {
+		for i := 1; i <= len(stop); i++ {
+			if strings.HasSuffix(sequence, stop[:i]) {
+				return true
+			}
+		}
+	}
+
+	return false
+}
+
+// truncateStop removes the provided stop string from pieces,
+// returning the partial pieces with stop removed, including truncating
+// the last piece if required (and signalling if this was the case)
+func TruncateStop(pieces []string, stop string) ([]string, bool) {
+	joined := strings.Join(pieces, "")
+
+	index := strings.Index(joined, stop)
+	if index == -1 {
+		return pieces, false
+	}
+
+	joined = joined[:index]
+
+	// Split truncated string back into pieces of original lengths
+	lengths := make([]int, len(pieces))
+	for i, piece := range pieces {
+		lengths[i] = len(piece)
+	}
+
+	var result []string
+	tokenTruncated := false
+	start := 0
+	for _, length := range lengths {
+		if start >= len(joined) {
+			break
+		}
+
+		end := start + length
+		if end > len(joined) {
+			end = len(joined)
+			tokenTruncated = true
+		}
+		result = append(result, joined[start:end])
+		start = end
+	}
+
+	return result, tokenTruncated
+}
+
+func IncompleteUnicode(token string) bool {
+	incomplete := false
+
+	// check if there is incomplete UTF-8 character at the end
+	for i := 1; i < 5 && i <= len(token); i++ {
+		c := token[len(token)-i]
+
+		if (c & 0xc0) == 0x80 {
+			// continuation byte: 10xxxxxx
+			continue
+		}
+
+		if (c & 0xe0) == 0xc0 {
+			// 2-byte character: 110xxxxx ...
+			incomplete = i < 2
+		} else if (c & 0xf0) == 0xe0 {
+			// 3-byte character: 1110xxxx ...
+			incomplete = i < 3
+		} else if (c & 0xf8) == 0xf0 {
+			// 4-byte character: 11110xxx ...
+			incomplete = i < 4
+		}
+
+		// else 1-byte character or invalid byte
+		break
+	}
+
+	return incomplete
+}

runner/common/stop_test.go

@@ -0,0 +1,129 @@
+package common
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestTruncateStop(t *testing.T) {
+	tests := []struct {
+		name          string
+		pieces        []string
+		stop          string
+		expected      []string
+		expectedTrunc bool
+	}{
+		{
+			name:          "Single word",
+			pieces:        []string{"hello", "world"},
+			stop:          "world",
+			expected:      []string{"hello"},
+			expectedTrunc: false,
+		},
+		{
+			name:          "Partial",
+			pieces:        []string{"hello", "wor"},
+			stop:          "or",
+			expected:      []string{"hello", "w"},
+			expectedTrunc: true,
+		},
+		{
+			name:          "Suffix",
+			pieces:        []string{"Hello", " there", "!"},
+			stop:          "!",
+			expected:      []string{"Hello", " there"},
+			expectedTrunc: false,
+		},
+		{
+			name:          "Suffix partial",
+			pieces:        []string{"Hello", " the", "re!"},
+			stop:          "there!",
+			expected:      []string{"Hello", " "},
+			expectedTrunc: true,
+		},
+		{
+			name:          "Middle",
+			pieces:        []string{"hello", " wor"},
+			stop:          "llo w",
+			expected:      []string{"he"},
+			expectedTrunc: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result, resultTrunc := TruncateStop(tt.pieces, tt.stop)
+			if !reflect.DeepEqual(result, tt.expected) || resultTrunc != tt.expectedTrunc {
+				t.Errorf("truncateStop(%v, %s): have %v (%v); want %v (%v)", tt.pieces, tt.stop, result, resultTrunc, tt.expected, tt.expectedTrunc)
+			}
+		})
+	}
+}
+
+func TestIncompleteUnicode(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected bool
+	}{
+		{
+			name:     "Basic",
+			input:    "hi",
+			expected: false,
+		},
+		{
+			name:     "Two byte",
+			input:    "hi" + string([]byte{0xc2, 0xa3}),
+			expected: false,
+		},
+		{
+			name:     "Two byte - missing last",
+			input:    "hi" + string([]byte{0xc2}),
+			expected: true,
+		},
+		{
+			name:     "Three byte",
+			input:    "hi" + string([]byte{0xe0, 0xA0, 0x80}),
+			expected: false,
+		},
+		{
+			name:     "Three byte - missing last",
+			input:    "hi" + string([]byte{0xe0, 0xA0}),
+			expected: true,
+		},
+		{
+			name:     "Three byte - missing last 2",
+			input:    "hi" + string([]byte{0xe0}),
+			expected: true,
+		},
+		{
+			name:     "Four byte",
+			input:    "hi" + string([]byte{0xf0, 0x92, 0x8a, 0xb7}),
+			expected: false,
+		},
+		{
+			name:     "Four byte - missing last",
+			input:    "hi" + string([]byte{0xf0, 0x92, 0x8a}),
+			expected: true,
+		},
+		{
+			name:     "Four byte - missing last 2",
+			input:    "hi" + string([]byte{0xf0, 0x92}),
+			expected: true,
+		},
+		{
+			name:     "Four byte - missing last 3",
+			input:    "hi" + string([]byte{0xf0}),
+			expected: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := IncompleteUnicode(tt.input)
+			if result != tt.expected {
+				t.Errorf("incompleteUnicode(%s): have %v; want %v", tt.input, result, tt.expected)
+			}
+		})
+	}
+}