analysis/acsetp.c, ac analysis, allow frequency=0

src/spicelib/analysis/acsetp.c

@@ -22,8 +22,8 @@ ACsetParm(CKTcircuit *ckt, JOB *anal, int which, IFvalue *value)
     switch(which) {
 
     case AC_START:
-	if (value->rValue <= 0.0) {
-	    errMsg = copy("Frequency of 0 is invalid for AC start");
+	if (value->rValue < 0.0) {
+	    errMsg = copy("Frequency of < 0 is invalid for AC start");
             job->ACstartFreq = 1.0;
 	    return(E_PARMVAL);
 	}
@@ -32,8 +32,8 @@ ACsetParm(CKTcircuit *ckt, JOB *anal, int which, IFvalue *value)
         break;
 
     case AC_STOP:
-	if (value->rValue <= 0.0) {
-	    errMsg = copy("Frequency of 0 is invalid for AC stop");
+	if (value->rValue < 0.0) {
+	    errMsg = copy("Frequency of < 0 is invalid for AC stop");
             job->ACstartFreq = 1.0;
 	    return(E_PARMVAL);
 	}

tests/regression/misc/Makefile.am

@@ -1,7 +1,7 @@
 ## Process this file with automake to produce Makefile.in
 
 
-TESTS = bugs-1.cir bugs-2.cir dollar-1.cir empty-1.cir resume-1.cir log-functions-1.cir alter-vec.cir test-noise-2.cir test-noise-3.cir
+TESTS = bugs-1.cir bugs-2.cir dollar-1.cir empty-1.cir resume-1.cir log-functions-1.cir alter-vec.cir test-noise-2.cir test-noise-3.cir ac-zero.cir
 
 TESTS_ENVIRONMENT = ngspice_vpath=$(srcdir) $(SHELL) $(top_srcdir)/tests/bin/check.sh $(top_builddir)/src/ngspice
 

tests/regression/misc/ac-zero.cir

@@ -0,0 +1,27 @@
+* whether .ac works for freq=0
+*
+* (exec-spice "ngspice -b %s" t)
+
+v1  1 0  dc=0 ac=1
+r1  1 2  1k
+l1  2 3  1uH
+r3  3 0  1k
+c3  3 0  1uF
+
+.control
+
+ac lin 1 0Hz 0Hz
+
+let v3_gold = 0.5
+
+let err = abs(v(3)/v3_gold - 1)
+
+if err > 1e-15
+  echo "ERROR: test failed, excessive error, err = $&err"
+  quit 1
+else
+  echo "INFO: success"
+  quit 0
+end
+
+.endc

tests/regression/misc/ac-zero.out

@@ -0,0 +1 @@
+INFO: success