1 files changed, 20 insertions, 0 deletions
diff --git a/src/misc.c b/src/misc.c
index 2f02595..bff0ba9 100644
--- a/src/misc.c
+++ b/src/misc.c
@@ -2,6 +2,26 @@
 #include <math.h>
 #include <stdlib.h> /* for size_t */
 
+double kahan_sum(double *x, size_t n)
+{
+    /* Returns the sum of the elements of `x` using the Kahan summation algorithm.
+     *
+     * See https://en.wikipedia.org/wiki/Kahan_summation_algorithm. */
+    size_t i;
+    double sum, c, y, t;
+
+    sum = 0.0;
+    c = 0.0;
+    for (i = 0; i < n; i++) {
+        y = x[i] - c;
+        t = sum + y;
+        c = (t - sum) - y;
+        sum = t;
+    }
+
+    return sum;
+}
+
 double interp1d(double x, double *xp, double *yp, size_t n)
 {
     /* A fast interpolation routine which assumes that the values in `xp` are