Add method to multiply dense vectors with CSC matrices

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

@@ -56,6 +56,22 @@ trait CSCMatrixOps extends CSCMatrixOps_Ring { this: CSCMatrix.type =>
       }
     }
 
+  implicit def canMulDVt_CSC_eq_DVt[T](
+      implicit op: OpMulMatrix.Impl2[DenseMatrix[T], CSCMatrix[T], DenseMatrix[T]],
+      zero: Zero[T],
+      ct: ClassTag[T]): OpMulMatrix.Impl2[Transpose[DenseVector[T]], CSCMatrix[T], Transpose[DenseVector[T]]] =
+    new OpMulMatrix.Impl2[Transpose[DenseVector[T]], CSCMatrix[T], Transpose[DenseVector[T]]] {
+      def apply(v: Transpose[DenseVector[T]], v2: CSCMatrix[T]): Transpose[DenseVector[T]] = {
+        require(v2.rows == v.inner.length)
+
+        val dm = v.inner.toDenseMatrix
+        val multiplied = op(dm, v2)
+
+        new Transpose[DenseVector[T]](multiplied.toDenseVector)
+
+      }
+    }
+
   @expand
   @expand.valify
   implicit def csc_OpNeg[@expand.args(Int, Double, Float, Long) T]: OpNeg.Impl[CSCMatrix[T], CSCMatrix[T]] = {

math/src/main/scala/breeze/linalg/DenseVector.scala

@@ -241,6 +241,14 @@ class DenseVector[@spec(Double, Int, Float, Long) V](
   def toScalaVector()(implicit cm: ClassTag[V]): scala.Vector[V] = this.toArray.toVector
   // </editor-fold>
 
+  def asCscRow(implicit man: ClassTag[V], zero: Zero[V]): CSCMatrix[V] = {
+    if (length == 0)
+      CSCMatrix.zeros[V](1, length)
+    else {
+      CSCMatrix.create(1, length, data)
+    }
+  }
+
   @throws(classOf[ObjectStreamException])
   protected def writeReplace(): Object = {
     new DenseVector.SerializedForm(data, offset, stride, length)
@@ -402,6 +410,23 @@ object DenseVector
     result
   }
 
+  def fromCSCMatrix[V: ClassTag](csc: CSCMatrix[V]): DenseVector[V] = {
+    assert(csc.rows == 1)
+    val indices = new Array[V](csc.cols)
+    var i = 0
+    while (i < csc.cols) {
+      var j = csc.colPtrs(i)
+      while (j < csc.colPtrs(i + 1)) {
+        indices(i) = csc.data(j)
+        j += 1
+      }
+      i += 1
+    }
+
+    DenseVector.create(indices, 0 ,1, csc.cols)
+
+  }
+
   // capabilities
 
   implicit def canCreateZerosLike[V: ClassTag: Zero]: CanCreateZerosLike[DenseVector[V], DenseVector[V]] =

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

@@ -589,6 +589,23 @@ class DenseVectorTest extends FunSuite with Checkers {
       assert(fromNew === slice)
     }
   }
+
+  test("#715 - transpose DV * CSCMatrix") {
+   val dv = DenseVector(1,2,3,4)
+
+    val csc = CSCMatrix.zeros[Int](4, 4)
+    csc(1, 1) = 1
+    csc(1, 2) = 2
+    csc(2, 1) = 2
+    csc(2, 2) = 4
+
+    val multiplied = dv.t * csc
+
+    val expected = DenseVector(0,8,16,0).t
+
+    assert(multiplied == expected)
+  }
+
 }
 
 abstract class DenseVectorPropertyTestBase[T: ClassTag] extends TensorSpaceTestBase[DenseVector[T], Int, T] {