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man pages->IRIX man pages -> complib/DTRCO (3)
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### Contents

```
DTRCO(3F)							     DTRCO(3F)

```

### NAME[Toc][Back]

```     DTRCO   - DTRCO estimates the condition of	a double precision triangular
matrix.

```

### SYNOPSYS[Toc][Back]

```      SUBROUTINE DTRCO(T,LDT,N,RCOND,Z,JOB)
```

### DESCRIPTION[Toc][Back]

```     On	Entry

T DOUBLE PRECISION(LDT,N)
T contains the triangular matrix.  The zero
elements of the	matrix are not referenced, and
the corresponding elements of the array	can be
used to	store other information.

LDT INTEGER
LDT is the leading dimension of	the array T.

N INTEGER
N is the order of the system.

JOB INTEGER
= 0	    T  is lower	triangular.
= nonzero   T  is upper	triangular.  On	Return

RCOND DOUBLE PRECISION
an estimate of the reciprocal condition	of  T .
For the	system	T*X = B	, relative perturbations
in  T  and  B  of size	EPSILON	 may cause
relative perturbations in  X  of size  EPSILON/RCOND .
If  RCOND  is so small that the	logical	expression
1.0 + RCOND .EQ. 1.0
is true, then  T  may be singular to working
precision.  In particular,  RCOND  is zero  if
exact singularity is detected or the estimate
underflows.

Z DOUBLE PRECISION(N)
a work vector whose contents are usually unimportant.
If  T  is close	to a singular matrix, then  Z  is
an approximate null vector in the sense	that
NORM(A*Z) = RCOND*NORM(A)*NORM(Z) .  LINPACK.  This version dated
08/14/78 .	 Cleve Moler, University of New	Mexico,	Argonne	National Lab.
Subroutines and Functions BLAS DAXPY,DSCAL,DASUM Fortran DABS,DMAX1,DSIGN

PPPPaaaaggggeeee 1111```
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