Implemented a stopping criterion.

git-svn-id: file:///home/svnrepos/software/liblbfgs/trunk@21 ecf4c44f-38d1-4fa4-9757-a0b4dd0349fc

include/lbfgs.h

@@ -74,6 +74,8 @@ typedef double lbfgsfloatval_t;
 enum {
     /** L-BFGS reaches convergence. */
     LBFGS_SUCCESS = 0,
+    LBFGS_CONVERGENCE = 0,
+    LBFGS_STOP,
     /** The initial variables already minimize the objective function. */
     LBFGS_ALREADY_MINIMIZED,
 
@@ -91,6 +93,12 @@ enum {
     LBFGSERR_INVALID_N_SSE,
     /** The array x must be aligned to 16 (for SSE). */
     LBFGSERR_INVALID_X_SSE,
+    /** Invalid parameter lbfgs_parameter_t::epsilon specified. */
+    LBFGSERR_INVALID_EPSILON,
+    /** Invalid parameter lbfgs_parameter_t::past specified. */
+    LBFGSERR_INVALID_TESTPERIOD,
+    /** Invalid parameter lbfgs_parameter_t::delta specified. */
+    LBFGSERR_INVALID_DELTA,
     /** Invalid parameter lbfgs_parameter_t::linesearch specified. */
     LBFGSERR_INVALID_LINESEARCH,
     /** Invalid parameter lbfgs_parameter_t::max_step specified. */
@@ -172,6 +180,9 @@ typedef struct {
      */
     lbfgsfloatval_t epsilon;
 
+    int             past;
+    lbfgsfloatval_t delta;
+
     /**
      * The maximum number of iterations.
      *  The lbfgs() function terminates an optimization process with