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- DOUBLE PRECISION FUNCTION DPMPAR (I)
- C-----------------------------------------------------------------------
- C
- C DPMPAR PROVIDES THE DOUBLE PRECISION MACHINE CONSTANTS FOR
- C THE COMPUTER BEING USED. IT IS ASSUMED THAT THE ARGUMENT
- C I IS AN INTEGER HAVING ONE OF THE VALUES 1, 2, OR 3. IF THE
- C DOUBLE PRECISION ARITHMETIC BEING USED HAS M BASE B DIGITS AND
- C ITS SMALLEST AND LARGEST EXPONENTS ARE EMIN AND EMAX, THEN
- C
- C DPMPAR(1) = B**(1 - M), THE MACHINE PRECISION,
- C
- C DPMPAR(2) = B**(EMIN - 1), THE SMALLEST MAGNITUDE,
- C
- C DPMPAR(3) = B**EMAX*(1 - B**(-T)), THE LARGEST MAGNITUDE.
- C
- C-----------------------------------------------------------------------
- C WRITTEN BY
- C ALFRED H. MORRIS, JR.
- C NAVAL SURFACE WARFARE CENTER
- C DAHLGREN VIRGINIA
- C-----------------------------------------------------------------------
- INTEGER EMIN, EMAX
- DOUBLE PRECISION B, BINV, BM1, ONE, W, Z
- C
- IF (I .GT. 1) GO TO 10
- B = IPMPAR(4)
- M = IPMPAR(8)
- DPMPAR = B**(1 - M)
- RETURN
- C
- 10 IF (I .GT. 2) GO TO 20
- B = IPMPAR(4)
- EMIN = IPMPAR(9)
- ONE = FLOAT(1)
- BINV = ONE/B
- W = B**(EMIN + 2)
- DPMPAR = ((W * BINV) * BINV) * BINV
- RETURN
- C
- 20 IBETA = IPMPAR(4)
- M = IPMPAR(8)
- EMAX = IPMPAR(10)
- C
- B = IBETA
- BM1 = IBETA - 1
- ONE = FLOAT(1)
- Z = B**(M - 1)
- W = ((Z - ONE)*B + BM1)/(B*Z)
- C
- Z = B**(EMAX - 2)
- DPMPAR = ((W * Z) * B) * B
- RETURN
- END
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