__device__ double tgamma ( double  x  ) 

Calculate the gamma function of the input argument x, namely the value of $\int_{0}^{\infty} e^{-t}t^{x-1}dt$.

Returns:
  • tgamma($\pm 0$) returns $\pm \infty$.
  • tgamma(2) returns +0.
  • tgamma(x) returns $\pm \infty$ if the correctly calculated value is outside the double floating point range.
  • tgamma(x) returns NaN if x < 0.
  • tgamma($-\infty$) returns NaN.
  • tgamma($+\infty$) returns $+\infty$.
Note:
For accuracy information for this function see the CUDA C Programming Guide, Appendix C, Table C-2.


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