fix for #850: transpose-slice-multiply crash

math/src/main/codegen/breeze/linalg/operators/DenseMatrixOps.scala

@@ -301,9 +301,9 @@ trait DenseMatrixMultiplyOps extends DenseMatrixExpandedOps with DenseMatrixMult
 
       // if we have a weird stride...
       val a: DenseMatrix[Double] =
-        if (_a.majorStride < math.max(if (_a.isTranspose) _a.cols else _a.rows, 1)) _a.copy else _a
+        if (_a.majorStride > math.max(if (_a.isTranspose) _a.cols else _a.rows, 1)) _a.copy else _a
       val b: DenseMatrix[Double] =
-        if (_b.majorStride < math.max(if (_b.isTranspose) _b.cols else _b.rows, 1)) _b.copy else _b
+        if (_b.majorStride > math.max(if (_b.isTranspose) _b.cols else _b.rows, 1)) _b.copy else _b
 
       blas.dgemm(
         transposeString(a),

math/src/test/scala/breeze/linalg/DenseMatrixTest.scala

@@ -846,6 +846,17 @@ class DenseMatrixTest extends AnyFunSuite with Checkers with DoubleImplicits wit
     assert(sm == sm.copy)
   }
 
+  test("#850 - transpose slice multiply bug") {
+    val Jɴ = DenseMatrix( (0.75,  -0.25), (-0.25,  0.75))
+    val matB = DenseMatrix(
+      (67.0, 33.0),
+      (69.0, 78.0),
+      (93.0, 57.0)
+    ).t
+    val B = matB(::, 1 until matB.cols)
+    Jɴ * B      // should not crash
+  }
+
 }
 
 trait MatrixTestUtils {

math/src/test/scala/breeze/linalg/TextOperationsTest.scala

@@ -7,9 +7,10 @@ import org.scalatest.funsuite.AnyFunSuite
  * Created by Luca Puggini: [email protected] on 19/02/16.
  */
 class TextOperationsTest extends AnyFunSuite {
+  System.err.println(new File(".").getAbsolutePath)
   test("csvread and String2File methods") {
     // A csv file can be read both using the java File function and the toFile method of the string class
-    val file_path = if (new File(".").getAbsolutePath.endsWith("math/.")) {
+    val file_path = if (new File(".").getAbsolutePath.replace('\\', '/').endsWith("math/.")) {
       "src/test/resources/glass_data.txt"
     } else {
       "./math/src/test/resources/glass_data.txt"

project/Build.scala

@@ -13,7 +13,7 @@ object Common {
     }
   }
 
-  val buildCrossScalaVersions = Seq("3.1.3", "2.12.15", "2.13.8")
+  val buildCrossScalaVersions = Seq("3.4.2", "2.12.19", "2.13.14")
 
   lazy val buildScalaVersion = buildCrossScalaVersions.head