matrix: imported matrix as a subtree

matrix/mat64/offset_appengine.go

@@ -0,0 +1,24 @@
+// Copyright ©2015 The gonum Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//+build appengine
+
+package mat64
+
+import "reflect"
+
+var sizeOfFloat64 = int(reflect.TypeOf(float64(0)).Size())
+
+// offset returns the number of float64 values b[0] is after a[0].
+func offset(a, b []float64) int {
+	va0 := reflect.ValueOf(a).Index(0)
+	vb0 := reflect.ValueOf(b).Index(0)
+	if va0.Addr() == vb0.Addr() {
+		return 0
+	}
+	// This expression must be atomic with respect to GC moves.
+	// At this stage this is true, because the GC does not
+	// move. See https://golang.org/issue/12445.
+	return int(vb0.UnsafeAddr()-va0.UnsafeAddr()) / sizeOfFloat64
+}