pow(x,y) returns 0 when x is very close to -1.0 and y is very large. Fix: freebsd: src/lib/msun/src/e_pow.c *** e_pow.c 1999/07/13 23:49:20 1.1 --- e_pow.c 2002/06/13 17:06:57 *************** How-To-Repeat: The following test program prints pow(1.0000000000000002e+00 4.5035996273704970e+15) = 2.7182818284590455e+00 pow(-1.0000000000000002e+00 4.5035996273704970e+15) = 0.0000000000000000e+00 pow(9.9999999999999978e-01 4.5035996273704970e+15) = 3.6787944117144222e-01 pow(-9.9999999999999978e-01 4.5035996273704970e+15) = 0.0000000000000000e+00 which is incorrect for the negative arguments raised to an odd integer power. double pow (double, double); int main () { double x, y, z; x = 1.0 + pow (2.0, -52.0); y = 1.0 + pow (2.0, 52.0); z = pow (x, y); printf ("pow(%.16e %.16e) = %.16e\n", x, y, z); x = -x; z = pow (x, y); printf ("pow(%.16e %.16e) = %.16e\n", x, y, z); x = 1.0 - pow (2.0, -52.0); z = pow (x, y); printf ("pow(%.16e %.16e) = %.16e\n", x, y, z); x = -x; z = pow (x, y); printf ("pow(%.16e %.16e) = %.16e\n", x, y, z); }
State Changed From-To: open->closed Patch applied in rev.1.9 (-current) and rev.1.6.2.1 (RELENG_4) of e_pow.c. Applied same patch to e_powf.c although it is just cosmetic there. Thanks.