From 88a68be227e1a9a833b313c969357bf3db07439f Mon Sep 17 00:00:00 2001
From: Mark Cianciosa <cianciosamr@ornl.gov>
Date: Tue, 15 Oct 2024 17:51:38 -0400
Subject: [PATCH] Test random number sequence by checking that autocorrelation
 is a delta function.

---
 test/CMakeLists.txt  |   1 +
 test/korc_test.f90   |  12 ++++-
 test/test_hpc.f90    |  11 +----
 test/test_random.f90 | 101 +++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 114 insertions(+), 11 deletions(-)
 create mode 100644 test/test_random.f90

diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 0d39adcd..16fbc64b 100755
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -8,6 +8,7 @@ target_sources(xtest
                $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/korc_test.f90>
                $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/test_io.f90>
                $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/test_hpc.f90>
+               $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/test_random.f90>
 )
 target_link_libraries (xtest
 
diff --git a/test/korc_test.f90 b/test/korc_test.f90
index 47935466..3dd9479d 100755
--- a/test/korc_test.f90
+++ b/test/korc_test.f90
@@ -2,11 +2,17 @@ program korc_test
   use fruit
   use test_io
   use test_hpc
+  use test_random
+  use korc_hpc, only : initialize_mpi,finalize_mpi
   implicit none
   logical ok
 
+  TYPE(KORC_PARAMS)           :: params
   CHARACTER(MX_STRING_LENGTH) :: path_to_outputs
   
+  params%path_to_inputs='TEST'
+  call initialize_mpi(params)
+
   ! create output file for testing
   call set_paths(path_to_outputs)
   
@@ -15,7 +21,8 @@ program korc_test
   
   ! run tests
   write(test_unit_write,*) 'Testing MPI initialization...'
-  call test_mpi_initialization
+  call test_mpi_initialization(params)
+  call test_random_auto
 
   ! compile summary and finalize fruit
   call fruit_summary(test_unit_write)
@@ -29,5 +36,6 @@ program korc_test
 
   close(test_unit_write)
 
-  
+  call finalize_mpi(params)
+
 end program korc_test
diff --git a/test/test_hpc.f90 b/test/test_hpc.f90
index 1fe32a47..efe2e225 100755
--- a/test/test_hpc.f90
+++ b/test/test_hpc.f90
@@ -6,17 +6,12 @@ module test_hpc
 
 contains
 
-  subroutine test_mpi_initialization
-    use korc_hpc, only : initialize_mpi,finalize_mpi
-    TYPE(KORC_PARAMS) :: params
+  subroutine test_mpi_initialization(params)
+    TYPE(KORC_PARAMS), INTENT(INOUT) :: params
     integer :: ierror
     integer :: size, rank
     integer :: size_k, rank_k
 
-    params%path_to_inputs='TEST'
-    
-    call initialize_mpi(params)
-
     size_k=params%mpi_params%nmpi
     rank_k=params%mpi_params%rank
 
@@ -25,8 +20,6 @@ subroutine test_mpi_initialization
 
     call assert_equals(size_k,size)
     call assert_equals(rank_k,rank)
-
-    call finalize_mpi(params)
     
   end subroutine test_mpi_initialization
 
diff --git a/test/test_random.f90 b/test/test_random.f90
new file mode 100644
index 00000000..13894a3c
--- /dev/null
+++ b/test/test_random.f90
@@ -0,0 +1,101 @@
+module test_random
+  use korc_random
+  use mpi
+  use fruit
+  implicit none
+
+contains
+
+  SUBROUTINE test_random_auto
+    IMPLICIT NONE
+
+!  Local Variables
+    CLASS (random_U_context), POINTER   :: uniform => null()
+    INTEGER                             :: mpierr
+    INTEGER                             :: i
+    INTEGER                             :: rank
+    INTEGER                             :: size
+    INTEGER                             :: localsize
+    REAL(rp), DIMENSION(:), ALLOCATABLE :: buffer
+    INTEGER, DIMENSION(:), ALLOCATABLE  :: counts
+    INTEGER, DIMENSION(:), ALLOCATABLE  :: offsets
+    REAL(rp)                            :: base
+    REAL(rp)                            :: test
+
+!  Local parameters
+    INTEGER, PARAMETER                  :: totalsize = 10000
+    INTEGER, PARAMETER                  :: window = totalsize/2
+
+!  Start of executable code.
+    call MPI_COMM_SIZE(MPI_COMM_WORLD, size, mpierr)
+    call MPI_COMM_RANK(MPI_COMM_WORLD, rank, mpierr)
+
+    IF (rank .eq. 0) THEN
+      WRITE (*,*)
+      WRITE (*,*) "Starting Random Test"
+    END IF
+
+    uniform => random_U_context_construct(0, rank)
+    CALL uniform%set(-1.0d0, 1.0d0)
+
+    localsize = totalsize/size
+    IF (rank .lt. MOD(totalsize, size)) THEN
+      localsize = localsize + 1
+    ENDIF
+
+    IF (rank .eq. 0) THEN
+      ALLOCATE(buffer(totalsize))
+      ALLOCATE(counts(size))
+      ALLOCATE(offsets(size))
+      CALL uniform%get_array(buffer(1:localsize))
+    ELSE
+      ALLOCATE(buffer(localsize))
+      CALL uniform%get_array(buffer)
+    END IF
+
+    CALL MPI_GATHER(localsize, 1, MPI_INTEGER,                                 &
+                    counts, 1, MPI_INTEGER,                                    &
+                    0, MPI_COMM_WORLD, mpierr)
+    IF (rank .eq. 0) THEN
+      offsets(1) = 0
+      DO i = 2, size
+        offsets(i) = offsets(i - 1)+counts(i - 1)
+      END DO
+    END IF
+    CALL MPI_GATHERV(buffer, localsize, MPI_DOUBLE,                            &
+                     buffer, counts, offsets, MPI_DOUBLE,                      &
+                     0, MPI_COMM_WORLD, mpierr)
+
+    IF (rank .eq. 0) THEN
+      DEALLOCATE(counts)
+      DEALLOCATE(offsets)
+
+!  Check against 10% of the first peak. We could go lower but I don't want to
+!  trigger a test failure on noise.
+      base = autocorrelation(buffer, 0)*0.1
+      DO i = 1, window
+        test = autocorrelation(buffer, i)
+        CALL assert_equals(test .gt. base, .false.)
+      END DO
+    END IF
+
+    DEALLOCATE(buffer)
+
+  END SUBROUTINE
+
+  FUNCTION autocorrelation(sequence, offset)
+
+    IMPLICIT NONE
+
+!  Declare arguments.
+    REAL(rp) :: autocorrelation
+    REAL(rp), DIMENSION(:) :: sequence
+    INTEGER                :: offset
+
+!  Start of executable code.
+    autocorrelation = DOT_PRODUCT(sequence(:SIZE(sequence) - offset),          &
+                                  sequence(offset + 1:))                       &
+                    / (SIZE(sequence) - offset)
+  END FUNCTION
+
+end module