calculate proper error estimate already when initializing integrator

It is no longer necessary to call `improve()` first.

1 files changed, 8 insertions, 6 deletions

diff --git a/vquad/core.py b/vquad/core.py
index a5e09b3..b9cc708 100644
--- a/vquad/core.py
+++ b/vquad/core.py
@@ -210,10 +210,9 @@ class Vquad:
         Mathematical Software, 37 (3), art. no. 26, 2008.
     """
 
-    def __init__(self, f, a, b, level=max_level - 1):
-        ival = _Interval(a, b, level, 1)
-        vals = f(ival.map(tbls.nodes[ival.level]))
-        ival.interpolate(vals)
+    def __init__(self, f, a, b, level=max_level):
+        ival = _Interval(a, b, level - 1, 1)
+        ival.interpolate(f(ival.map(tbls.nodes[level - 1])))
         ival.c00 = 0.0          # Will go away.
         ival.ndiv = 0
 
@@ -228,6 +227,10 @@ class Vquad:
         ival.next = self.end = _Terminator()
         self.end.prev = ival
 
+        # Refine up to requested level.  This calculates a proper error
+        # estimate.
+        self.improve()
+
     def improve(self):
         ival = self.ivals[-1]
 
@@ -278,14 +281,13 @@ class Vquad:
             raise ValueError("Either rtol or atol must be nonzero.")
 
         while True:
-            self.improve()
             igral, err = self.totals()
-
             tol = max(atol, abs(igral) * rtol)
             if (err == 0 or err < tol
                 or self.err_excess > tol > err - self.err_excess
                 or not self.ivals):
                 return igral, err
+            self.improve()
 
     def __call__(self, xs):
         xs = np.asarray(xs)