# csyl01.f - Man Page

TESTING/EIG/csyl01.f

## Synopsis

### Functions/Subroutines

subroutine **csyl01** (thresh, nfail, rmax, ninfo, knt)**CSYL01**

## Function/Subroutine Documentation

### subroutine csyl01 (real thresh, integer, dimension( 3 ) nfail, real, dimension( 2 ) rmax, integer, dimension( 2 ) ninfo, integer knt)

**CSYL01**

**Purpose:**

CSYL01 tests CTRSYL and CTRSYL3, routines for solving the Sylvester matrix equation op(A)*X + ISGN*X*op(B) = scale*C, where op(A) and op(B) are both upper triangular form, op() represents an optional conjugate 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 CGET35 by testing with larger, random matrices, of which some require rescaling of X to avoid overflow.

**Parameters***THRESH*THRESH is REAL 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 CTRSYL exceeds threshold THRESH NFAIL(2) = No. of times residual CTRSYL3 exceeds threshold THRESH NFAIL(3) = No. of times CTRSYL3 and CTRSYL deviate

*RMAX*RMAX is DOUBLE PRECISION array, dimension (2) RMAX(1) = Value of the largest test ratio of CTRSYL RMAX(2) = Value of the largest test ratio of CTRSYL3

*NINFO*NINFO is INTEGER array, dimension (2) NINFO(1) = No. of times CTRSYL where INFO is nonzero NINFO(2) = No. of times CTRSYL3 where INFO is nonzero

*KNT*KNT is INTEGER Total number of examples tested.

Definition at line **88** of file **csyl01.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page csyl01(3) is an alias of csyl01.f(3).

Tue Nov 28 2023 12:08:42 Version 3.12.0 LAPACK