---
name: "dlamch"
section: "3lapack"
platform: "linux"
package: "liblapack-doc"
version: "3.2.1-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/dlamch/3lapack"
---

# dlamch(3lapack)

double precision machine parameters

## NAME

DLAMCH - double precision machine parameters

## SYNOPSIS

- DOUBLE PRECISION

  FUNCTION DLAMCH( CMACH )

- CHARACTER

  CMACH

## PURPOSE

DLAMCH determines double precision machine parameters.

## ARGUMENTS

- CMACH (input) 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)