clean up + add examples with NaN and concurrent call

Author: HugoMVale

example/stats_distribution_exponential/example_exponential_cdf.f90

@@ -4,38 +4,61 @@ program example_exponential_cdf
                                                    rexp => rvs_exp
 
   implicit none
-  real :: x(2, 3, 4), a(2, 3, 4)
+  real, dimension(2, 3, 4) :: x, lambda
+  real :: xsum
   complex :: scale
-  integer :: seed_put, seed_get
+  integer :: seed_put, seed_get, i
 
   seed_put = 1234567
   call random_seed(seed_put, seed_get)
 
-  print *, exp_cdf(1.0, 1.0)  ! a standard exponential cumulative at 1.0
+  ! standard exponential cumulative distribution at x=1.0
+  print *, exp_cdf(1.0, 1.0)
+  ! 0.632120550
 
-! 0.632120550
+  ! cumulative distribution at x=2.0 with lambda=2
+  print *, exp_cdf(2.0, 2.0)
+  ! 0.981684387
 
-  print *, exp_cdf(2.0, 2.0) ! a cumulative at 2.0 with lambda=2
-
-! 0.981684387
+  ! cumulative distribution at x=2.0 with lambda=-1.0 (out of range)
+  print *, exp_cdf(2.0, -1.0) 
+  ! NaN
 
+   ! standard exponential random variates array
   x = reshape(rexp(0.5, 24), [2, 3, 4])
-! standard exponential random variates array
-  a(:, :, :) = 0.5
-  print *, exp_cdf(x, a)  ! a rank 3 array of standard exponential cumulative
 
-!  8.57694745E-02  9.70223546E-02  1.52170658E-02  2.95336246E-02
-!  0.107568979  0.196659625  2.97447443E-02  0.366151094  0.163051903
-!  3.36527228E-02  0.385267735  0.428375721  0.103964329  0.147119939
-!  0.192206264  0.330693483  0.179247737  2.92580128E-02  0.332765043
-!  0.472417951  0.500440359  8.56802464E-02  8.72612000E-03  3.55126858E-02
+  ! a rank-3 exponential cumulative distribution
+  lambda(:, :, :) = 0.5
+  print *, exp_cdf(x, lambda)
+  ! 0.301409245  0.335173965  5.94930053E-02  0.113003314
+  ! 0.365694344  0.583515942  0.113774836     0.838585377
+  ! 0.509324908  0.127967060  0.857194781     0.893231630
+  ! 0.355383813  0.470882893  0.574203610     0.799321830
+  ! 0.546216846  0.111995399  0.801794767     0.922525287
+  ! 0.937719882  0.301136374  3.44503522E-02  0.134661376 
+
+  ! cumulative distribution array where lambda<=0.0 for certain elements 
+  print *, exp_cdf([1.0, 1.0, 1.0], [1.0, 0.0, -1.0])
+  ! 0.632120550  NaN NaN
+
+  ! `cdf_exp` is pure and, thus, can be called concurrently 
+  xsum = 0.0
+  do concurrent (i=1:size(x,3))
+    xsum = xsum + sum(exp_cdf(x(:,:,i), lambda(:,:,i)))
+  end do
+  print *, xsum
+  ! 11.0886612
 
+  ! complex exponential cumulative distribution at (0.5,0.5) with real part of
+  ! lambda=0.5 and imaginary part of lambda=1.0
   scale = (0.5, 1.0)
   print *, exp_cdf((0.5, 0.5), scale)
-!complex exponential cumulative distribution at (0.5,0.5) with real part of
-!lambda=0.5 and imaginary part of lambda=1.0
+  ! 8.70351046E-02
 
-! 8.70351046E-02
+  ! As above, but with lambda%im < 0 
+  scale = (1.0, -2.0)
+  print *, exp_cdf((1.5, 1.0), scale)
+  ! NaN
 
 end program example_exponential_cdf