# dlamch.f - Man Page

INSTALL/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 precision a, double precision b)

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..

Parameters

A

`          A is a DOUBLE PRECISION`

B

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

Definition at line 171 of file dlamch.f.

### double precision function dlamch (character cmach)

DLAMCH

Purpose:

` DLAMCH determines double precision machine parameters.`
Parameters

CMACH

```          CMACH is CHARACTER*1
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

NAG Ltd.

Definition at line 68 of file dlamch.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man pages dlamc3(3) and dlamch(3) are aliases of dlamch.f(3).

Tue Nov 28 2023 12:08:41 Version 3.12.0 LAPACK