native,cgo: update docs for Dgehrd

Author: vladimir-ch

cgo/lapack.go

@@ -565,15 +565,17 @@ func (impl Implementation) Dgeqrf(m, n int, a []float64, lda int, tau, work []fl
 // -1 if n == 0, otherwise Dgehrd will panic.
 //
 // On return, tau will contain the scalar factors of the elementary reflectors.
-// Elements tau[:ilo] and tau[ihi:] of tau will be set to zero. It must have
-// length equal to n-1 if n > 1, otherwise Dgehrd will panic.
+// Elements tau[:ilo] and tau[ihi:] will be set to zero. tau must have length
+// equal to n-1 if n > 0, otherwise Dgehrd will panic.
 //
-// work must have length at least lwork, otherwise Dgehrd will panic, and lwork
-// must be at least max(1,n).
+// work must have length at least lwork and lwork must be at least max(1,n),
+// otherwise Dgehrd will panic. On return, work[0] contains the optimal value of
+// lwork.
 //
-// The C interface does not support providing temporary storage. To provide
-// compatibility with native, lwork == -1 will not run Dgehrd but will instead
-// write the minimum work necessary to work[0].
+// If lwork == -1, instead of performing Dgehrd, only the optimal value of lwork
+// will be stored in work[0].
+//
+// Dgehrd is an internal routine. It is exported for testing purposes.
 func (impl Implementation) Dgehrd(n, ilo, ihi int, a []float64, lda int, tau, work []float64, lwork int) {
 	checkMatrix(n, n, a, lda)
 	switch {

native/dgehrd.go

@@ -54,14 +54,17 @@ import (
 // -1 if n == 0, otherwise Dgehrd will panic.
 //
 // On return, tau will contain the scalar factors of the elementary reflectors.
-// Elements tau[:ilo] and tau[ihi:] of tau will be set to zero. It must have
-// length equal to n-1 if n > 1, otherwise Dgehrd will panic.
+// Elements tau[:ilo] and tau[ihi:] will be set to zero. tau must have length
+// equal to n-1 if n > 0, otherwise Dgehrd will panic.
 //
-// work must have length at least lwork, otherwise Dgehrd will panic, and lwork
-// must be at least max(1,n). On return, work[0] contains the optimal value of lwork.
+// work must have length at least lwork and lwork must be at least max(1,n),
+// otherwise Dgehrd will panic. On return, work[0] contains the optimal value of
+// lwork.
 //
-// If lwork is -1, instead of performing Dgehrd, the function only calculates
-// the optimal length of work.
+// If lwork == -1, instead of performing Dgehrd, only the optimal value of lwork
+// will be stored in work[0].
+//
+// Dgehrd is an internal routine. It is exported for testing purposes.
 func (impl Implementation) Dgehrd(n, ilo, ihi int, a []float64, lda int, tau, work []float64, lwork int) {
 	checkMatrix(n, n, a, lda)
 	switch {