native: address review comments

native/dgeqrf.go

@@ -14,20 +14,21 @@ import (
 // parameters at entry and exit.
 //
 // work is temporary storage, and lwork specifies the usable memory length.
-// At minimum, lwork >= max(1, m) and this function will panic otherwise.
+// The length of work must be at least max(1, lwork) and lwork must be -1
+// or at least n, otherwise this function will panic.
 // Dgeqrf is a blocked QR factorization, but the block size is limited
 // by the temporary space available. If lwork == -1, instead of performing Dgeqrf,
 // the optimal work length will be stored into work[0].
 //
 // tau must have length at least min(m,n), and this function will panic otherwise.
 func (impl Implementation) Dgeqrf(m, n int, a []float64, lda int, tau, work []float64, lwork int) {
+	if len(work) < max(1, lwork) {
+		panic(shortWork)
+	}
 	// nb is the optimal blocksize, i.e. the number of columns transformed at a time.
 	nb := impl.Ilaenv(1, "DGEQRF", " ", m, n, -1, -1)
 	lworkopt := n * max(nb, 1)
 	lworkopt = max(n, lworkopt)
-	if len(work) < max(1, lwork) {
-		panic(shortWork)
-	}
 	if lwork == -1 {
 		work[0] = float64(lworkopt)
 		return