dlamch.f -

## SYNOPSIS

### Functions/Subroutines

DOUBLE PRECISION function dlamch (CMACH)
DLAMCH
DOUBLE PRECISION function dlamc3 (A, B)
DLAMC3

## Function/Subroutine Documentation

### DOUBLE PRECISION function dlamc3 (double precisionA, double precisionB)

DLAMC3 Purpose:

``` DLAMC3  is intended to force  A  and  B  to be stored prior to doing
the addition of  A  and  B ,  for use in situations where optimizers
might hold one of these in a register.
```

Author:

LAPACK is a software package provided by Univ. of Tennessee, Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..

Date:

November 2011

Parameters:

A

```          A is a DOUBLE PRECISION
```

B

```          B is a DOUBLE PRECISION
The values A and B.
```

Definition at line 172 of file dlamch.f.

### DOUBLE PRECISION function dlamch (characterCMACH)

DLAMCH Purpose:

``` DLAMCH determines double precision machine parameters.
```

Parameters:

CMACH

```          Specifies the value to be returned by DLAMCH:
= 'E' or 'e',   DLAMCH := eps
= 'S' or 's ,   DLAMCH := sfmin
= 'B' or 'b',   DLAMCH := base
= 'P' or 'p',   DLAMCH := eps*base
= 'N' or 'n',   DLAMCH := t
= 'R' or 'r',   DLAMCH := rnd
= 'M' or 'm',   DLAMCH := emin
= 'U' or 'u',   DLAMCH := rmin
= 'L' or 'l',   DLAMCH := emax
= 'O' or 'o',   DLAMCH := rmax
where
eps   = relative machine precision
sfmin = safe minimum, such that 1/sfmin does not overflow
base  = base of the machine
prec  = eps*base
t     = number of (base) digits in the mantissa
rnd   = 1.0 when rounding occurs in addition, 0.0 otherwise
emin  = minimum exponent before (gradual) underflow
rmin  = underflow threshold - base**(emin-1)
emax  = largest exponent before overflow
rmax  = overflow threshold  - (base**emax)*(1-eps)
```

Author:

Univ. of Tennessee

Univ. of California Berkeley