native: clean up Dormqr

native/dormqr.go

@@ -15,8 +15,8 @@ import (
 //  C = Q^T * C  if side == blas.Left and trans == blas.Trans
 //  C = C * Q    if side == blas.Right and trans == blas.NoTrans
 //  C = C * Q^T  if side == blas.Right and trans == blas.Trans
-// If side == blas.Left, A is a matrix of side k×m, and if side == blas.Right
+// If side == blas.Left, A is a matrix of side m×k, and if side == blas.Right
-// A is of size k×n. This uses a blocked algorithm.
+// A is of size n×k. This uses a blocked algorithm.
 //
 // work is temporary storage, and lwork specifies the usable memory length.
 // At minimum, lwork >= m if side == blas.Left and lwork >= n if side == blas.Right,
@@ -28,28 +28,47 @@ import (
 // tau contains the Householder scales and must have length at least k, and
 // this function will panic otherwise.
 func (impl Implementation) Dormqr(side blas.Side, trans blas.Transpose, m, n, k int, a []float64, lda int, tau, c []float64, ldc int, work []float64, lwork int) {
-	left := side == blas.Left
+	var nq, nw int
-	notran := trans == blas.NoTrans
+	switch side {
-	if left {
+	default:
-		checkMatrix(m, k, a, lda)
+		panic(badSide)
-	} else {
+	case blas.Left:
-		checkMatrix(n, k, a, lda)
+		nq = m
+		nw = n
+	case blas.Right:
+		nq = n
+		nw = m
 	}
+	switch {
+	case trans != blas.NoTrans && trans != blas.Trans:
+		panic(badTrans)
+	case m < 0 || n < 0:
+		panic(negDimension)
+	case k < 0 || nq < k:
+		panic("lapack: invalid value of k")
+	case len(work) < lwork:
+		panic(shortWork)
+	case lwork < max(1, nw) && lwork != -1:
+		panic(badWork)
+	}
+	if lwork != -1 {
+		checkMatrix(nq, k, a, lda)
 		checkMatrix(m, n, c, ldc)
-
 		if len(tau) < k {
 			panic(badTau)
 		}
+	}
+
+	if m == 0 || n == 0 || k == 0 {
+		work[0] = 1
+		return
+	}
 
 	const (
 		nbmax = 64
 		ldt   = nbmax
-		tsize = nbmax * nbmax
+		tsize = nbmax * ldt
 	)
-	nw := n
-	if side == blas.Right {
-		nw = m
-	}
 	opts := string(side) + string(trans)
 	nb := min(nbmax, impl.Ilaenv(1, "DORMQR", opts, m, n, k, -1))
 	lworkopt := max(1, nw)*nb + tsize
@@ -57,35 +76,27 @@ func (impl Implementation) Dormqr(side blas.Side, trans blas.Transpose, m, n, k
 		work[0] = float64(lworkopt)
 		return
 	}
-	if len(work) < lwork {
-		panic(badWork)
-	}
-	if left {
-		if lwork < n {
-			panic(badWork)
-		}
-	} else {
-		if lwork < m {
-			panic(badWork)
-		}
-	}
-	if m == 0 || n == 0 || k == 0 {
-		return
-	}
-	nbmin := 2
 
-	if nb > 1 && nb < k {
+	nbmin := 2
+	if 1 < nb && nb < k {
 		if lwork < nw*nb+tsize {
 			nb = (lwork - tsize) / nw
 			nbmin = max(2, impl.Ilaenv(2, "DORMQR", opts, m, n, k, -1))
 		}
 	}
-	if nb < nbmin || nb >= k {
+
+	if nb < nbmin || k <= nb {
 		// Call unblocked code.
 		impl.Dorm2r(side, trans, m, n, k, a, lda, tau, c, ldc, work)
+		work[0] = float64(lworkopt)
 		return
 	}
-	ldwork := nb
+
+	var (
+		ldwork = nb
+		left   = side == blas.Left
+		notran = trans == blas.NoTrans
+	)
 	switch {
 	case left && notran:
 		for i := ((k - 1) / nb) * nb; i >= 0; i -= nb {
@@ -143,4 +154,5 @@ func (impl Implementation) Dormqr(side blas.Side, trans blas.Transpose, m, n, k
 				work[tsize:], ldwork)
 		}
 	}
+	work[0] = float64(lworkopt)
 }