fixed dependencies

vendor/gonum.org/v1/gonum/mat/shadow_common.go

@@ -0,0 +1,54 @@
+// 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.
+
+package mat
+
+const (
+	// regionOverlap is the panic string used for the general case
+	// of a matrix region overlap between a source and destination.
+	regionOverlap = "mat: bad region: overlap"
+
+	// regionIdentity is the panic string used for the specific
+	// case of complete agreement between a source and a destination.
+	regionIdentity = "mat: bad region: identical"
+
+	// mismatchedStrides is the panic string used for overlapping
+	// data slices with differing strides.
+	mismatchedStrides = "mat: bad region: different strides"
+)
+
+// rectanglesOverlap returns whether the strided rectangles a and b overlap
+// when b is offset by off elements after a but has at least one element before
+// the end of a. off must be positive. a and b have aCols and bCols respectively.
+//
+// rectanglesOverlap works by shifting both matrices left such that the left
+// column of a is at 0. The column indexes are flattened by obtaining the shifted
+// relative left and right column positions modulo the common stride. This allows
+// direct comparison of the column offsets when the matrix backing data slices
+// are known to overlap.
+func rectanglesOverlap(off, aCols, bCols, stride int) bool {
+	if stride == 1 {
+		// Unit stride means overlapping data
+		// slices must overlap as matrices.
+		return true
+	}
+
+	// Flatten the shifted matrix column positions
+	// so a starts at 0, modulo the common stride.
+	aTo := aCols
+	// The mod stride operations here make the from
+	// and to indexes comparable between a and b when
+	// the data slices of a and b overlap.
+	bFrom := off % stride
+	bTo := (bFrom + bCols) % stride
+
+	if bTo == 0 || bFrom < bTo {
+		// b matrix is not wrapped: compare for
+		// simple overlap.
+		return bFrom < aTo
+	}
+
+	// b strictly wraps and so must overlap with a.
+	return true
+}