From 33f133fad3d881a6cc736c7221e81ee810ae29ab Mon Sep 17 00:00:00 2001
From: Kei Okada <k-okada@jsk.t.u-tokyo.ac.jp>
Date: Sun, 8 Apr 2018 17:55:55 +0900
Subject: [PATCH] if normalize-vector takes zero vector, return zero vector
 instead of nan vector

---
 lisp/c/matrix.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/lisp/c/matrix.c b/lisp/c/matrix.c
index 7e46a6035..f748023c0 100644
--- a/lisp/c/matrix.c
+++ b/lisp/c/matrix.c
@@ -308,6 +308,9 @@ register pointer argv[];
   for (i=0; i<s; i++) sum+= a[i]*a[i];
   sum=sqrt(sum);
   for (i=0; i<s; i++) r[i]=a[i]/sum;
+  int all_nan=1; /* if all element is nan, return 0 vector */
+  for (i=0; i<s; i++) if (!isnan(r[i])) all_nan=0; // false
+  if (all_nan) for (i=0; i<s; i++) r[i]=0;
   return(result);}
   
 pointer VDISTANCE(ctx,n,argv)