dsyl01.f - Man Page

subroutine dsyl01 (thresh, nfail, rmax, ninfo, knt)
DSYL01

DSYL01

Purpose:

 DSYL01 tests DTRSYL and DTRSYL3, routines for solving the Sylvester matrix
 equation

    op(A)*X + ISGN*X*op(B) = scale*C,

 A and B are assumed to be in Schur canonical form, op() represents an
 optional transpose, and ISGN can be -1 or +1.  Scale is an output
 less than or equal to 1, chosen to avoid overflow in X.

 The test code verifies that the following residual does not exceed
 the provided threshold:

    norm(op(A)*X + ISGN*X*op(B) - scale*C) /
        (EPS*max(norm(A),norm(B))*norm(X))

 This routine complements DGET35 by testing with larger,
 random matrices, of which some require rescaling of X to avoid overflow.

Parameters

THRESH

          THRESH is DOUBLE PRECISION
          A test will count as 'failed' if the residual, computed as
          described above, exceeds THRESH.

NFAIL

          NFAIL is INTEGER array, dimension (3)
          NFAIL(1) = No. of times residual DTRSYL exceeds threshold THRESH
          NFAIL(2) = No. of times residual DTRSYL3 exceeds threshold THRESH
          NFAIL(3) = No. of times DTRSYL3 and DTRSYL deviate

RMAX

          RMAX is DOUBLE PRECISION, dimension (2)
          RMAX(1) = Value of the largest test ratio of DTRSYL
          RMAX(2) = Value of the largest test ratio of DTRSYL3

NINFO

          NINFO is INTEGER array, dimension (2)
          NINFO(1) = No. of times DTRSYL returns an expected INFO
          NINFO(2) = No. of times DTRSYL3 returns an expected INFO

KNT

          KNT is INTEGER
          Total number of examples tested.

Definition at line 88 of file dsyl01.f.