Merge pull request #1308 from stan-dev/change-default-sig-figs

Change default sig_figs value to 8

Author: WardBrian

src/cmdstan/arguments/arg_output_sig_figs.hpp

@@ -10,17 +10,21 @@ class arg_output_sig_figs : public int_argument {
   arg_output_sig_figs() : int_argument() {
     _name = "sig_figs";
     _description
-        = "The number of significant figures used for the output CSV files.";
-    _validity
-        = "0 <= integer <= 18 or -1 to use the default number of significant "
-          "figures";
-    _default = "-1";
-    _default_value = -1;
+        = "The number of significant figures used for the output CSV files. "
+          "Stan recommends at least 8 (the default) if you will be using the "
+          "output as part of a future input (e.g., for standalone generated "
+          "quantities or as an initialization). If -1 is supplied, Stan will "
+          "use the current operating system's default precision (This "
+          "typically be smaller than Stan's default; on many systems it is 6 "
+          "digits).";
+    _validity = "0 <= sig_figs <= 18 || sig_figs == -1";
+    _default = "8";
+    _default_value = 8;
     _value = _default_value;
   }
 
   bool is_valid(int value) {
-    return (value >= 0 && value <= 18) || value == _default_value;
+    return (value >= 0 && value <= 18) || value == -1;
   }
 };