Expm1Tests.java revision 2362
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*
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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*
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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*/
/*
* @test
* @bug 4851638 4900189 4939441
* @summary Tests for {Math, StrictMath}.expm1
* @author Joseph D. Darcy
*/
/*
* The Taylor expansion of expxm1(x) = exp(x) -1 is
*
* 1 + x/1! + x^2/2! + x^3/3| + ... -1 =
*
* x + x^2/2! + x^3/3 + ...
*
* Therefore, for small values of x, expxm1 ~= x.
*
* For large values of x, expxm1(x) ~= exp(x)
*
* For large negative x, expxm1(x) ~= -1.
*/
public class Expm1Tests {
private Expm1Tests(){}
static int testExpm1() {
int failures = 0;
double [][] testCases = {
{-infinityD, -1.0},
{-0.0, -0.0},
{+0.0, +0.0},
};
// Test special cases
}
// For |x| < 2^-54 expm1(x) ~= x
failures += testExpm1Case(d, d);
failures += testExpm1Case(-d, -d);
}
// For values of y where exp(y) > 2^54, expm1(x) ~= exp(x).
// The least such y is ln(2^54) ~= 37.42994775023705; exp(x)
// overflows for x > ~= 709.8
// Use a 2-ulp error threshold to account for errors in the
// exp implementation; the increments of d in the loop will be
// exact.
for(double d = 37.5; d <= 709.5; d += 1.0) {
}
// For x > 710, expm1(x) should be infinity
}
// By monotonicity, once the limit is reached, the
// implemenation should return the limit for all smaller
// values.
boolean reachedLimit [] = {false, false};
// Once exp(y) < 0.5 * ulp(1), expm1(y) ~= -1.0;
// The greatest such y is ln(2^-53) ~= -36.7368005696771.
for(double d = -36.75; d >= -127.75; d -= 1.0) {
}
}
// Test for monotonicity failures near multiples of log(2).
// Test two numbers before and two numbers after each chosen
// value; i.e.
//
// pcNeighbors[] =
// {nextDown(nextDown(pc)),
// nextDown(pc),
// pc,
// nextUp(pc),
// nextUp(nextUp(pc))}
//
// and we test that expm1(pcNeighbors[i]) <= expm1(pcNeighbors[i+1])
{
double pcNeighbors[] = new double[5];
double pcNeighborsExpm1[] = new double[5];
double pcNeighborsStrictExpm1[] = new double[5];
for(int i = -50; i <= 50; i++) {
}
failures++;
pcNeighbors[j] + " and " +
pcNeighborsExpm1[j] + " and " +
pcNeighborsExpm1[j+1] );
}
failures++;
pcNeighbors[j] + " and " +
pcNeighborsStrictExpm1[j] + " and " +
pcNeighborsStrictExpm1[j+1] );
}
}
}
}
return failures;
}
public static int testExpm1Case(double input,
double expected) {
}
public static int testExpm1CaseWithUlpDiff(double input,
double expected,
double ulps,
boolean [] reachedLimit) {
int failures = 0;
double mathOutput;
double strictOutput;
if (reachedLimit != null) {
if (reachedLimit[0])
mathUlps = 0;
if (reachedLimit[1])
strictUlps = 0;
}
if (reachedLimit != null) {
}
return failures;
}
int failures = 0;
if (failures > 0) {
+ failures + " failures.");
throw new RuntimeException();
}
}
}