refine logic for na, nan and inf processing.

include/LightGBM/utils/common.h

@@ -8,6 +8,7 @@
 #include <vector>
 #include <sstream>
 #include <cstdint>
+#include <algorithm>
 
 namespace LightGBM {
 
@@ -140,35 +141,24 @@ inline static const char* Atof(const char* p, double* out) {
     // Return signed and scaled floating point result.
     *out = sign * (frac ? (value / scale) : (value * scale));
   } else {
-    if (*p == 'n' || *p == 'N') {
-      ++p;
-      if (!(*p == 'a' || *p == 'A')) {
-        Log::Stderr("meet error while parsing string to float, expect a nan here");
-      }
-      ++p;
-      if (!(*p == 'n' || *p == 'N')) {
-        Log::Stderr("meet error while parsing string to float, expect a nan here");
-      }
-      ++p;
-      // default convert nan to 0
+    size_t cnt = 0;
+    while (*(p + cnt) != '\0' && *(p + cnt) != ' ' 
+      && *(p + cnt) != '\t' && *(p + cnt) != ','
+      && *(p + cnt) != '\n' && *(p + cnt) != '\r'
+      && *(p + cnt) != ':')  {
+      ++cnt;
+    }
+    std::string tmp_str(p, cnt);
+    std::transform(tmp_str.begin(), tmp_str.end(), tmp_str.begin(), ::tolower);
+    if (tmp_str == std::string("na") || tmp_str == std::string("nan")) {
       *out = 0;
-    } else if (*p == 'i' || *p == 'I') {
-      ++p;
-      if (!(*p == 'n' || *p == 'N')) {
-        Log::Stderr("meet error while parsing string to float, expect a inf here");
-      }
-      ++p;
-      if (!(*p == 'f' || *p == 'F')) {
-        Log::Stderr("meet error while parsing string to float, expect a inf here");
-      }
-      ++p;
-      // default inf
+    } else if( tmp_str == std::string("inf") || tmp_str == std::string("infinity")) {
       *out = sign * 1e308;
-    } else {
-      if (*p != '\0') {
-        Log::Stderr("Meet unknow characters while parsing string to float");
     }
+    else {
+      Log::Stderr("Unknow token %s in data file", tmp_str.c_str());
     }
+    p += cnt;
   }
 
   while (*p == ' ') {