HYPOT

This functions computes SQRT(A**2 + B**2) without underflow or overflow.

Function Return Value

HYPOT — SQRT(A**2 + B**2). (Output)

Required Arguments

A — First parameter. (Input)

B — Second parameter. (Input)

FORTRAN 90 Interface

Generic: HYPOT (A, B)

Specific: The specific interface names are S_HYPOT and D_HYPOT.

FORTRAN 77 Interface

Single: HYPOT (A, B)

Double: The double precision name is DHYPOT.

Description

Routine HYPOT is based on the routine PYTHAG, used in EISPACK 3. This is an update of the work documented in Garbow et al. (1972).

Example

Computes

 

where a = 1020 and b = 2 × 1020 without overflow.

 

USE HYPOT_INT

USE UMACH_INT

 

IMPLICIT NONE

! Declare variables

INTEGER NOUT

REAL A, B, C

!

A = 1.0E+20

B = 2.0E+20

C = HYPOT(A,B)

! Get output unit number

CALL UMACH (2, NOUT)

! Print the results

WRITE (NOUT,'(A,1PE10.4)') ' C = ', C

END

Output

 

C = 2.2361E+20