Bigint - limited bit size

[neil]

Ive tried the test program and found when multiplying the two input numbers (a x b) the bit size seems to be limited to 50 bits, and when forming the factorial it's limited to 150 bits. Perhaps I've missed something in the implementation, but i just used the filed from Sourceforge and rand the test program with a few numbers. Thanks for any suggestions, Neil

[Alex Vinokur]

Hi,

Could you send your test?

Alex

[neil]

Thanks for your rapid response.

From your good code i have:

int
main(int argc, char** argv) {
BigInt a("-99999999"), b(10000000), c;
c = a * b;
cout << endl << a << " * " << b << " = " << c << endl;
c = a % b;
cout << endl << a << " % " << b << " = " << c << endl;
string s = "39";
c = BigInt::factorial(s);
cout << endl << s << " !" << " = " << c << endl;
return 0;
}

which generates the output:
-99999999 * 10000000 = 99999990000000
-99999999 % 10000000 = -9999999
39 ! = 2606625904899470449481415313618422988800000000
RUN SUCCESSFUL (total time: 130ms)

which is great.

However, when i increase a by an extra character '9' as in:
BigInt a("-999999999"), b(10000000), c;

i get:
RUN FAILED (exit value -1,073,741,819, total time: 5s)

and when i increase the factorial number by one, as in:
string s = "40";

i get:

-99999999 * 10000000 = 99999990000000

-99999999 % 10000000 = -9999999

40 ! = 0

RUN SUCCESSFUL (total time: 120ms)

But factorial 40 isn't zero, so something amiss somewhere.

many thanks for any help,
neil

[Alex Vinokur]

Hi,

Compilation of your main() failed on my compiler (g++ version 4.9.2).

error: no matching function for call to ‘BigInt::BigInt(const char [10])’
BigInt a("-99999999"), b(10000000), c;

error: ‘factorial’ is not a member of ‘BigInt’
c = BigInt::factorial(s);

---

Which version of C++ BigInt are you using?

Latest version is 5.0.

https://sourceforge.net/projects/cpp-bigint/files/C%2B%2B%20BigInt%20Class/Version%205.0/

---

Which compiler are you using?

[neil]

[neil]

Again thank you for the help. A couple of days ago i downloaded what i though was the most recent version, but looking in the file header it did say February 2011.

However, from your above link i downloaded the files from version 5.0 bigInt.f, bigInt.cpp and main.cpp. They compiled without errors, but on running the code i get several thousand lines of hex data with TURE and FALSE words dotted around, then ending with the statement:
RUN FAILED (exit value 1, total time: 4s)

Somehow i don't think this is quite how it should be.

Cheers,
neil

[Alex Vinokur]

‘factorial’ is not a member of ‘BigInt’

How can it be compiled?

[Alex Vinokur]

My C++ BigInt doesn't print RUN FAILED or RUN SUCCESSFUL