Updating the computation of SNR to handle non-positive values.

src/stcal/ramp_fitting/src/slope_fitter.c

@@ -2058,6 +2058,7 @@ ols_slope_fit_pixels(
                 ret = 1;
                 goto END;
             }
+            // goto END; /* XXX REMOVED THIS!!! */
         }
     }
 
@@ -2217,6 +2218,7 @@ ramp_fit_pixel(
         ret = 1;
         goto END;
     }
+    // dbg_ols_print("(%ld, %ld) median rate = %f\n", pr->row, pr->col, pr->median_rate);
 
     /* Clean up any thing from the last pixel ramp */
     clean_segment_list(pr->nints, pr->segs);
@@ -2328,15 +2330,15 @@ ramp_fit_pixel_integration_fit_slope(
     /* Fit slope to each segment. */
     for (current = pr->segs[integ].head; current; current = current->flink) {
         segcnt++;
+#if 0
+        dbg_ols_print("   *** [%ld] (%ld, %ld) Seg: %d, Length: %ld, Start: %ld, End: %ld\n",
+            integ, pr->row, pr->col, segcnt, current->length, current->start, current->end);
+#endif
         ret = ramp_fit_pixel_integration_fit_slope_seg(
                     current, rd, pr, current, integ, segcnt);
         if (-1 == ret) {
             continue;
         }
-#if 0
-        dbg_ols_print("   *** [%ld] (%ld, %ld) Seg: %d, Length: %ld, Start: %ld, End: %ld\n",
-            integ, pr->row, pr->col, segcnt, current->length, current->start, current->end);
-#endif
 
         invvar_r += (1. / current->var_r);
         if (pr->median_rate > 0.) {
@@ -2394,17 +2396,17 @@ ramp_fit_pixel_integration_fit_slope_seg(
 {
     // dbg_ols_print("[%ld] segnum = %d, length = %ld\n", integ, segnum, current->length);
     if (1 == current->length) {
-        //dbg_ols_print("(%ld, %ld) Segment %d has length 1\n", pr->row, pr->col, segnum);
+        // dbg_ols_print("(%ld, %ld) Segment %d has length 1\n", pr->row, pr->col, segnum);
         rd->special1++;
         return ramp_fit_pixel_integration_fit_slope_seg_len1(
                 rd, pr, current, integ, segnum);
     } else if (2 == current->length) {
-        //dbg_ols_print("(%ld, %ld) Segment %d has length 2\n", pr->row, pr->col, segnum);
+        // dbg_ols_print("(%ld, %ld) Segment %d has length 2\n", pr->row, pr->col, segnum);
         rd->special2++;
         return ramp_fit_pixel_integration_fit_slope_seg_len2(
                     rd, pr, current, integ, segnum);
     }
-    //dbg_ols_print("(%ld, %ld) Segment %d has length >2\n", pr->row, pr->col, segnum);
+    // dbg_ols_print("(%ld, %ld) Segment %d has length >2\n", pr->row, pr->col, segnum);
 
     return ramp_fit_pixel_integration_fit_slope_seg_default(
                     rd, pr, current, integ, segnum);
@@ -2783,7 +2785,6 @@ segment_snr(
 {
     npy_intp idx_s, idx_e;
     float data, num, den, S, start, end;
-    //char * msg = NULL;
 
     idx_s = get_ramp_index(rd, integ, seg->start);
     idx_e = idx_s + seg->length - 1;
@@ -2792,17 +2793,8 @@ segment_snr(
     data = end - start;
     den = pr->rnoise * pr->rnoise + data * pr->gain;
 
-    if (den < 0.) {
-        /* XXX
-         * Not sure if this exception should be here.
-         * If not exception could set snr to -1. as an
-         * indication of failure.
-         */
-        // msg = "SNR denominator is less than or equal to zero";
-        //PyErr_SetString(PyExc_ValueError, msg);
-        //err_ols_print("(%ld, %ld) %s\n", pr->row, pr->col, msg);
-        *snr = -1.;
-        return 1;
+    if (0.0 == den) {
+        *snr = 0.;
     } else {
         num = data * pr->gain;
         S = num / sqrt(den);