From a2f54963b625669d867411bdb444b062b7bb2d0b Mon Sep 17 00:00:00 2001
From: Jiaming Yuan <jm.yuan@outlook.com>
Date: Wed, 15 Apr 2020 17:47:57 +0800
Subject: [PATCH] Write binary header. (#5532)

---
 src/learner.cc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/learner.cc b/src/learner.cc
index 1c0e91dea..835ea4ad2 100644
--- a/src/learner.cc
+++ b/src/learner.cc
@@ -777,7 +777,8 @@ class LearnerIO : public LearnerConfiguration {
       }
       extra_attr.emplace_back("metrics", os.str());
     }
-
+    std::string header {"binf"};
+    fo->Write(header.data(), 4);
     fo->Write(&mparam, sizeof(LearnerModelParamLegacy));
     fo->Write(tparam_.objective);
     fo->Write(tparam_.booster);