Author: alarantalara
Date: Mon Mar 26 07:01:16 2012
New Revision: 53663
URL: http://svn.gna.org/viewcvs/wesnoth?rev=53663&view=rev
Log:
switch effect multiplication to double and add extensive comment (re: r53615)
Modified:
trunk/src/unit_abilities.cpp
Modified: trunk/src/unit_abilities.cpp
URL:
http://svn.gna.org/viewcvs/wesnoth/trunk/src/unit_abilities.cpp?rev=53663&r1=53662&r2=53663&view=diff
==============================================================================
--- trunk/src/unit_abilities.cpp (original)
+++ trunk/src/unit_abilities.cpp Mon Mar 26 07:01:16 2012
@@ -882,15 +882,23 @@
effect_list_.push_back(set_effect);
}
- float multiplier = 1.0f;
- float divisor = 1.0f;
+ /* Do multiplication with floating point values rather than integers
+ * We want two places of precision for each multiplier
+ * Using integers multiplied by 100 to keep precision causes overflow
+ * after 3-4 abilities for 32-bit values and ~8 for 64-bit
+ * Avoiding the overflow by dividing after each step introduces
rounding errors
+ * that may vary depending on the order effects are applied
+ * As the final values are likely <1000 (always true for mainline),
loss of less significant digits is not an issue
+ */
+ double multiplier = 1.0;
+ double divisor = 1.0;
std::map<std::string,individual_effect>::const_iterator e, e_end;
for (e = values_mul.begin(), e_end = values_mul.end(); e != e_end; ++e)
{
- multiplier *= e->second.value/100.0f;
+ multiplier *= e->second.value/100.0;
effect_list_.push_back(e->second);
}
for (e = values_div.begin(), e_end = values_div.end(); e != e_end; ++e)
{
- divisor *= e->second.value/100.0f;
+ divisor *= e->second.value/100.0;
effect_list_.push_back(e->second);
}
int addition = 0;
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