few optimizations for diode recombination current calculation

src/spicelib/devices/dio/dioload.c

@@ -46,7 +46,7 @@ DIOload(GENmodel *inModel, CKTcircuit *ckt)
     double evd;
     double evrev;
     double gd, gdb, gdsw, gen_fac, gen_fac_vd;
-    double evd_rec, cdb_rec, gdb_rec;
+    double t1, evd_rec, cdb_rec, gdb_rec;
     double geq;
     double gspr;    /* area-scaled conductance */
     double sarg;
@@ -235,15 +235,18 @@ next1:      if (model->DIOsatSWCurGiven) {              /* sidewall current */
                 evd = exp(vd/vte);
                 cdb = csat*(evd-1);
                 gdb = csat*evd/vte;
-                evd_rec = exp(vd/(model->DIOrecEmissionCoeff*vt)); /* recombination current */
-                cdb_rec = here->DIOtRecSatCur*(evd_rec-1);
-                gdb_rec = here->DIOtRecSatCur*evd_rec/vt;
-                gen_fac = pow((pow((1-vd/here->DIOtJctPot), 2) + 0.005), here->DIOtGradingCoeff/2);
-                gen_fac_vd = here->DIOtGradingCoeff * (1-vd/here->DIOtJctPot) * pow((pow((1-vd/here->DIOtJctPot), 2) + 0.005), here->DIOtGradingCoeff/2-1);
-                cdb_rec = cdb_rec * gen_fac;
-                gdb_rec = gdb_rec * gen_fac + cdb_rec * gen_fac_vd;
-                cdb = cdb + cdb_rec;
-                gdb = gdb + gdb_rec;
+                if (model->DIOrecSatCurGiven) { /* recombination current */
+                    evd_rec = exp(vd/(model->DIOrecEmissionCoeff*vt));
+                    cdb_rec = here->DIOtRecSatCur*(evd_rec-1);
+                    gdb_rec = here->DIOtRecSatCur*evd_rec/vt;
+                    t1 = pow((1-vd/here->DIOtJctPot), 2) + 0.005;
+                    gen_fac = pow(t1, here->DIOtGradingCoeff/2);
+                    gen_fac_vd = here->DIOtGradingCoeff * (1-vd/here->DIOtJctPot) * pow(t1, (here->DIOtGradingCoeff/2-1));
+                    cdb_rec = cdb_rec * gen_fac;
+                    gdb_rec = gdb_rec * gen_fac + cdb_rec * gen_fac_vd;
+                    cdb = cdb + cdb_rec;
+                    gdb = gdb + gdb_rec;
+                }
 
             } else if((!(model->DIObreakdownVoltageGiven)) ||
                     vd >= -here->DIOtBrkdwnV) { /* reverse */