optimize/functions: implement the many local minima functions in the virtual library of simulation experiments

optimize/functions/doc.go

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+// Copyright ©2017 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.
+
+// Package functions provides objective functions for testing optimization
+// algorithms.
+//
+// We encourage outside contributions of additional test functions that exhibit
+// properties not already covered in the testing suite or that have
+// significance due to prior use as benchmark cases.
+package functions // import "gonum.org/v1/gonum/optimize/functions"
+
+const (
+	badInputDim = "functions: wrong input dimension"
+)