# dlamch.f man page

dlamch.f —

## Synopsis

### Functions/Subroutines

DOUBLE PRECISION functiondlamch(CMACH)DLAMCH

DOUBLE PRECISION functiondlamc3(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

Univ. of Colorado Denver

NAG Ltd.

**Date:**

November 2011

Definition at line 64 of file dlamch.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

dlamc3(3) and dlamch(3) are aliases of dlamch.f(3).