[LNT] Make baseline colour closer to the sample than its neighbour

[Yi Kong]

Hi Chris,

Baseline plot is currently quite confusing. Second baseline and those
after has color is irrelevant to the sample it's comparing to. The
patch should make them more distinguishable by setting baseline colour
closer to the sample than its neighbour.

For comparison:
http://llvm.org/perf/db_default/v4/nts/graph?plot.426=34.426.2&plot.412=34.412.2&plot.214=34.214.2&baseline.b=19898&baseline.b2=19899

http://noncsg.doc.ic.ac.uk:55088/db_default/v4/nts/graph?plot.169=3.169.3&plot.170=3.170.3&plot.171=3.171.3&baseline.b=19&baseline.b2=21

-Yi
-------------- next part --------------
Index: lnt/server/ui/views.py
===================================================================
--- lnt/server/ui/views.py	(revision 212105)
+++ lnt/server/ui/views.py	(working copy)
@@ -565,10 +565,9 @@
         # Aggregate by revision.
         data = util.multidict((rev, (val, date)) for val,rev,date in q).items()
         data.sort(key=lambda sample: convert_revision(sample[0]))
-        color_offset = 1
         # Get baselines for this line
         num_baselines = len(baseline_parameters)
-        for baseline, baseline_title in baseline_parameters:
+        for baseline_id, (baseline, baseline_title) in enumerate(baseline_parameters):
             q_baseline = ts.query(field.column, ts.Order.llvm_project_revision, ts.Run.start_time, ts.Machine.name).\
                          join(ts.Run).join(ts.Order).join(ts.Machine).\
                          filter(ts.Run.id == baseline.id).\
@@ -583,8 +582,9 @@
                 continue
             mean = sum(samples)/len(samples)
             # Darken the baseline color distinguish from non-baselines.
-            # Make a color spread that is wide enough for all baselines x plots.
-            my_color = (float(i) * num_baselines + color_offset) / (num_plots * num_baselines)
+            # Make a color closer to the sample than its neighbour.
+            color_offset = float(baseline_id) / num_baselines / 2
+            my_color = (i + color_offset) / num_plots
             dark_col = list(util.makeDarkerColor(my_color))
             str_dark_col =  util.toColorString(dark_col)
             baseline_plots.append({'color': str_dark_col,
@@ -593,7 +593,7 @@
                                    'name': q_baseline[0].llvm_project_revision})
             baseline_name = "Baseline {} on {}".format(baseline_title,  q_baseline[0].name)
             legend.append((BaselineLegendItem(baseline_name, baseline.id), test.name, field.name, dark_col))
-            color_offset += 1
+
         # Compute the graph points.
         errorbar_data = []
         points_data = []