liyunzhang_intel created PIG-4265:
-------------------------------------
Summary: AlgebraicDoubleMathBase has "Java double precision
problems"
Key: PIG-4265
URL: https://issues.apache.org/jira/browse/PIG-4265
Project: Pig
Issue Type: Bug
Reporter: liyunzhang_intel
$PIG_HOME/bin/pig -x local RubyUDFs_10.pig
#RubyUDFs_10.pig
register '/home/zly/prj/oss/pig/bin/libexec/ruby/scriptingudfs.rb' using jruby
as myfuncs;
a = load 'studenttab10k' using PigStorage() as (name, age:int, gpa:double);
b = group a by name;
c = foreach b generate group, myfuncs.Sum(a.age), myfuncs.Sum(a.gpa);
d = foreach c generate $0, $1, (double)((int)$2*100)/100;
store d into 'RubyUDFs_10.out';
the result in RubyUDFs_10.out/part
#grep "david s" RubyUDFs_10.out/part-r-00000
david steinbeck 266 15.0
#grep "david s" studenttab10k
david steinbeck 21 2.44
david steinbeck 33 1.17
david steinbeck 42 1.94
david steinbeck 42 1.35
david steinbeck 31 2.77
david steinbeck 40 2.42
david steinbeck 57 3.91
when you sum all the gpa of "david steinbeck" in the file "studenttab10k", the
result is "16" while the result in RubyUDFs_10.out/part-r-00000 is "15". The
reason is because double precision problem in AlgebraicDoubleMathBase.java.
It sums all the gpa numbers to 15.999999-(double)((int)15.999999*100)/100 =
15.0.
{code}
AlgebraicDoubleMathBase.java
private static Double doWork(Double arg1, Double arg2, KNOWN_OP op) {
if (arg1 == null) {
return arg2;
} else if (arg2 == null) {
return arg1;
} else {
switch (op) {
case MAX: return Math.max(arg1, arg2);
case MIN: return Math.min(arg1, arg2);
case SUM: return arg1+arg2; //this line has "Java BigDecimal
precision problem"
default: return null;
}
}
}
{code}
The detail Java double precision problem you can refer
"https://community.oracle.com/thread/2448849?tstart=0";
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