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This package provides a drop in replacement for Go's built in math/big big integer package using the GNU Multiprecision Library (GMP).

GMP is very much faster than Go's math/big however it is an external C library with all the problems that entails (cgo, dependencies etc)

This library was made by taking the cgo example of wrapping GMP from the Go source and doing the following to it

  • Copying the implementation from misc/cgo/gmp/gmp.go
  • Copying the documentation from src/pkg/math/big/int.go
  • Additional implementation of missing methods
  • Bug fixes for existing implementations
  • Making it passes the test suite from src/pkg/math/big/int_test.go
  • Adding memory management
  • Fix problems on 32 bit platforms when using int64 values which don't fit into a C.long
  • Implementing Rat support making it pass src/pkg/math/big/rat_test.go

See here for package docs


Use go to install the library

go get


See here for full package docs

To use as in a drop in replacement for math/big, replace

import "math/big"


import big ""

Features that aren't part of math/big are clearly marked and if you are using those, then I suggest you import as

import ""


To run the tests use

go test

The tests have been copied from the tests for the math/big library in the Go source and modified as little as possible so it should be 100% compatible.


Here are the differences between math/big and this package

  • Int.Bits and Int.SetBits not implemented
  • Rat.Num() and Rat.Denom() return a copy not a reference, so
  • If you want to set them use the new methods Rat.SetNum() and Rat.SetDenom()


As this contains a great deal of code copied from the Go source it is licenced identically to the Go source itself - see the LICENSE file for details.

Contact and support

The project website is at:

There you can file bug reports, ask for help or contribute patches.



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