[lmi-commits] [lmi] master 061fa21 3/3: Round {ee, er}-apportioned net premium, preserving their total

[Greg Chicares]

branch: master
commit 061fa216bf330b3314f7e1639fab6a5617db2961
Author: Gregory W. Chicares <gchicares@sbcglobal.net>
Commit: Gregory W. Chicares <gchicares@sbcglobal.net>

    Round {ee,er}-apportioned net premium, preserving their total
---
 ihs_avmly.cpp | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/ihs_avmly.cpp b/ihs_avmly.cpp
index 6869c47..d91f358 100644
--- a/ihs_avmly.cpp
+++ b/ihs_avmly.cpp
@@ -284,7 +284,17 @@ void AccountValue::process_payment(double payment)
         {
         er_proportion = ErGrossPmts[Month] / gross_non_1035_pmts;
         }
-    double er_net_pmt = er_proportion * payment;
+
+    // This is a net premium that's multiplied by a gross-premium
+    // proportion, because that's the only way the proportion can be
+    // deduced from input. But it remains a net premium, so the
+    // net-premium rounding rule is appropriate.
+    double er_net_pmt = round_net_premium()(er_proportion * payment);
+    // This is deliberately not rounded. The crucial invariant that
+    // must be preserved is that ee + er = total; but rounding both
+    // addends could break that invariant, e.g.:
+    //   round(2.5) + round(2.5)
+    // might not produce 5.0 as desired.
     double ee_net_pmt = payment - er_net_pmt;
 
     switch(ee_premium_allocation_method)