fix devious assumption in searchsorted that if searching a length one array it assumed the array was meant to be in descending order; it now assumes ascending order and this assumption is documented.

1 files changed, 6 insertions, 2 deletions

diff --git a/src/sorting.h b/src/sorting.h
index 03eabc6..9fd52fe 100644
--- a/src/sorting.h
+++ b/src/sorting.h
@@ -55,6 +55,10 @@ piksrt2(int n, T *arr, U *brr)
     }
 }
 
+/* Returns the index in `arr` where `x` should be inserted in order to
+   maintain order. If `n` equals one, return the index such that, when
+   `x` is inserted, `arr` will be in ascending order.
+*/
 template <class T>
 __device__ unsigned long
 searchsorted(unsigned long n, T *arr, const T &x)
@@ -65,12 +69,12 @@ searchsorted(unsigned long n, T *arr, const T &x)
     jl = 0;
     ju = n;
 
-    ascnd = (arr[n-1] > arr[0]);
+    ascnd = (arr[n-1] >= arr[0]);
 
     while (ju-jl > 1) {
 	jm = (ju+jl) >> 1;
 
-	if (x >= arr[jm] == ascnd)
+	if ((x > arr[jm]) == ascnd)
 	    jl = jm;
 	else
 	    ju = jm;