complex function c8lgmc (zin) c may 1978 edition. w. fullerton, c3, los alamos scientific lab. c c compute the log gamma correction term for almost all z so that c clog(cgamma(z)) = 0.5*alog(2.*pi) + (z-0.5)*clog(z) - z + c8lgmc(z) c this routine is valid even when real(z) is negative or when cabs(z) c is small. c when real(z) is negative, c8lgmc merely returns a correction which c may be wrong by a multiple of 2*pi*i. c complex zin, z, corr, c9lgmc, c0lgmc, cexp, clnrel external c0lgmc, c9lgmc, clnrel, 1 r1mach data pi / 3.1415926535 8979324e0 / data bound, sqeps, eps / 3*0.0 / c if (bound.ne.0.0) go to 10 nterm = -0.30*alog(r1mach(3)) bound = 0.1170*float(nterm)* 1 (0.1*r1mach(3))**(-1.0/(2.0*float(nterm)-1.0)) eps = 10.0*r1mach(4) sqeps = sqrt (r1mach(4)) c 10 z = zin x = real(z) y = aimag(z) if (x.lt.0.0) z = -z c corr = (0.0, 0.0) if (x.gt.bound .or. abs(y).ge.bound) go to 30 cabsz = cabs(z) if (cabsz.ge.bound) go to 30 c if (x.eq.0.0 .and. y.eq.0.0) call seteru ( 1 57hc8lgmc log gamma correction term is infinite for z = 0.0, 2 57, 3, 2) c n = sqrt (bound**2-y**2) - abs(x) + 1.0 do 20 i=1,n corr = corr + c0lgmc(z) z = z + 1.0 20 continue c 30 c8lgmc = c9lgmc(z) + corr if (x.gt.0.0) return c call entsrc (irold, 1) test = 1.0 if (x.lt.(-0.5)) test = cabs ((z-aint(x-0.5))/z) if (test.lt.eps) call seteru ( 1 31hc8lgmc z is a negative integer, 31, 2, 2) c z = zin if (y.lt.0.0) z = conjg(z) corr = -cmplx(0.0,pi) + clnrel(-cexp(cmplx(0.,2.*pi)*z)) if (y.lt.0.0) corr = conjg(corr) c c8lgmc = corr - c8lgmc c call erroff call entsrc (ir, irold) if (test.lt.sqeps) call seteru ( 63hc8lgmc answer lt half precisi 1on, z too near a negative integer, 63, 1, 1) c return end