Gamma random number generator support only integer shape parameter.

Describe the bug Trying to call rand() from a ExponentialFamilyMixture object results in the following exception:

[E] Exception in thread "main" java.lang.IllegalArgumentException: Gamma random number generator support only integer shape parameter. [E] at smile.stat.distribution.GammaDistribution.rand(GammaDistribution.java:155) [E] at smile.stat.distribution.Mixture.rand(Mixture.java:194)

Expected behavior Expected random variate from Mixture model.

Actual behavior

The algorithm throws an exception. Here is the stack trace:

Code snippet

val days = List(6, 14, 197, 483, 502, 193, 221, 122, 252, 145, 266, 312, 284, 172, 744, 150, 664, 289, 451, 180)
val a = new Mixture.Component(0.3, new GaussianDistribution(0.0, 1.0))
val b = new Mixture.Component(0.3, new ExponentialDistribution(1.0))
val c = new Mixture.Component(0.4, new GammaDistribution(1.0, 2.0))
val kernel = ExponentialFamilyMixture.fit(days.map(_.toDouble).toArray, a, b, c)
println(kernel.rand())

Input data List(6, 14, 197, 483, 502, 193, 221, 122, 252, 145, 266, 312, 284, 172, 744, 150, 664, 289, 451, 180)

Additional context

Java: 17.0.7 from GraalVM
Scala: 3.3.0
Lib versions: "com.github.haifengl" %% "smile-scala" % "3.0.2", "org.bytedeco" % "javacpp-platform" % "1.5.9", "org.bytedeco" % "openblas-platform" % "0.3.23-1.5.9", "org.bytedeco" % "arpack-ng-platform" % "3.9.0-1.5.9"
What is your build system: MacOS (M1, macosx-arm64)

haifengl / smile

Gamma random number generator support only integer shape parameter. #746