java - BigDecimal.add strange behavior -


method bigdecimal.add takes long time when 1 argument has big exponent (9 digits), , second has exponent different length. i've waited more 5 minutes, , still going on , on.

here's code:

@test public void testaddbig() throws exception {     mathcontext mc = new mathcontext(10, roundingmode.half_up);     bigdecimal v1 = new bigdecimal("1e+100000000", mc);     bigdecimal v2 = new bigdecimal("1", mc);     system.out.println(v1.add(v2)); }

here's part of thread dump:

at java.math.biginteger.square(biginteger.java:1884) @ java.math.biginteger.squarekaratsuba(biginteger.java:1975) @ java.math.biginteger.square(biginteger.java:1888) @ java.math.biginteger.squaretoomcook3(biginteger.java:2011) @ java.math.biginteger.square(biginteger.java:1890) @ java.math.biginteger.squaretoomcook3(biginteger.java:2006) @ java.math.biginteger.square(biginteger.java:1890) @ java.math.biginteger.squaretoomcook3(biginteger.java:2012) @ java.math.biginteger.square(biginteger.java:1890) @ java.math.biginteger.squaretoomcook3(biginteger.java:2010) @ java.math.biginteger.square(biginteger.java:1890) @ java.math.biginteger.squaretoomcook3(biginteger.java:2006) @ java.math.biginteger.square(biginteger.java:1890) @ java.math.biginteger.squaretoomcook3(biginteger.java:2012) @ java.math.biginteger.square(biginteger.java:1890) @ java.math.biginteger.squaretoomcook3(biginteger.java:2011) @ java.math.biginteger.square(biginteger.java:1890) @ java.math.biginteger.pow(biginteger.java:2263) @ java.math.bigdecimal.bigtentothe(bigdecimal.java:3543) @ java.math.bigdecimal.bigmultiplypowerten(bigdecimal.java:4508) @ java.math.bigdecimal.add(bigdecimal.java:4443) @ java.math.bigdecimal.add(bigdecimal.java:1289)

what going on? bug?

well, answer simply. bignumbers working array of character keep precision @ maximum. since number composed of 100000000 digits, length of array.

100.000.000 chars = bytes

this 100mb if not mistaken. want math that, start lot of reading ;)

if open bigdecimal class, see there lot of checks since "letter" , not numbers.

bigdecimal usefull keep precision done @ cost, here memory , time of processing.

edit :

this problem if use instance in ways, constructor store value exponent value 1e+***. if print fine if ask numerical value, start failed.

to more precise, bigdecimal.bigtentothe(int) receive exponent value (1000000000).

private static biginteger bigtentothe(int n) {     ...     char tenpow[] = new char[n + 1];     .... }

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