◆ rpqr79()

Roots of a polynomial (real coefficients) (Companion matrix eigenvalues)

Purpose: rpqr79 computes all roots of a polynomial p(z) with real coefficients by computing the eigenvalues of the companion matrix.
p(z) = a0*z^n + a1*z^(n-1) + ... + an

Parameters

[in]	n	Degree of polynomial (n >= 1)
[in]	a[]	Array a[la] (la >= n + 1) Real coefficient vector of p(z) (a0 to an).
[out]	r[]	Array r[lr] (lr >= n) The obtained zeros.
[out]	work[]	Array work[lwork] Work array.
[in]	lwork	Size of work array. (lwork >= n*(n + 13))
[out]	info	= 0: Successful exit = -1: The argument n had an illegal value (n < 1) = -2: The argument a had an illegal value (a[0] = 0) = -5: The argument lwork had an illegal value (lwork too small) = 1: Failed to converge QR iteration on some eigenvalue of the companion matrix