+
+
+double diff_aux(lmm_variable_t var, double x)
+{
+ double tmp_fpi, result;
+
+ XBT_IN2("(var (%p), x (%1.20f))", var, x);
+ xbt_assert0(var->func_fpi,
+ "Initialize the protocol functions first create variables before.");
+
+ tmp_fpi = var->func_fpi(var, x);
+ result = - tmp_fpi;
+
+ XBT_OUT;
+ return result;
+}
+
+
+/**************** Vegas and Reno functions *************************/
+/*
+ * NOTE for Reno: all functions consider the network
+ * coeficient (alpha) equal to 1.
+ */
+
+/*
+ * For Vegas fpi: $\frac{\alpha D_f}{x}$
+ */
+double func_vegas_fpi(lmm_variable_t var, double x){
+ xbt_assert0(x>0.0,"Don't call me with stupid values!");
+ return VEGAS_SCALING*var->df/x;
+}
+
+/*
+ * For Reno fpi: $\sqrt{\frac{1}{{D_f}^2 x} - \frac{2}{3{D_f}^2}}$
+ */
+double func_reno_fpi(lmm_variable_t var, double x){
+ double res_fpi;
+
+ xbt_assert0(var->df>0.0,"Don't call me with stupid values!");
+ xbt_assert0(x>0.0,"Don't call me with stupid values!");
+
+ res_fpi = 1/(var->df*var->df*x) - 2/(3*var->df*var->df);
+ if(res_fpi<=0.0) return 0.0;
+ xbt_assert0(res_fpi>0.0,"Don't call me with stupid values!");
+ return sqrt(res_fpi);
+}
+