#

A Tour of NTL: Obtaining and Installing NTL for UNIX

This procedure should work on most Unix or Unix-like platorms (including Mac OSX, and Windows with Cygwin tools).

To obtain the source code and documentation for NTL, download `ntl-xxx.tar.gz`, placing it a directory, and then, working in this directory, do the following. Here, "`xxx`" denotes the current version number.

       % gunzip ntl-xxx.tar.gz
       % tar xf ntl-xxx.tar
       % cd ntl-xxx/src
       % ./configure PREFIX=$HOME/sw
       % make
       % make check
       % make install

This will build, test, and install NTL in `$HOME/sw`. Of course, change `$HOME/sw` to whatever you want (the default is `/usr/local`). You will find the NTL header files in `$HOME/sw/include/NTL` and the compiled binary in `$HOME/sw/lib/libntl.a` (this is a static library -- if you want a shared library, see below).

If you really are interested in high-performace, you will definitely want to build NTL using GMP (the GNU Multi-Precision package). If GMP has already been installed in a standard place, like `/usr/local`, then invoke `configure` above as

       % ./configure PREFIX=$HOME/sw NTL_GMP_LIP=on

and if GMP is installed somewhere else, say `$HOME/sw`, then either

       % ./configure PREFIX=$HOME/sw NTL_GMP_LIP=on GMP_PREFIX=$HOME/sw

or, more simply,

       % ./configure DEF_PREFIX=$HOME/sw NTL_GMP_LIP=on

does the job. Here, `DEF_PREFIX` is a variable that is used to specify the location of all software, and it defaults to `/usr/local`. This page provides more details.

If you want very high-performance for polynomial arithmetic over GF(2), you may want to consider using the `gf2x` library. To do this, `gf2x` must already be installed somewhere. In addition, you should invoke `configure` with the option `NTL_GF2X_LIB=on`. If `gf2x` is installed in a standard location, this is all you need to do; otherwise, if `gf2x` is installed, say, in `$HOME/sw`, then you also need to pass the option `GF2X_PREFIX=$HOME/sw`. This page provides more details.

Now suppose you want to compile a program that uses NTL. Suppose you are working in some directory and `foo.c` is your program. Assume that you have installed NTL in `$HOME/sw` as above. The following should work:

       % g++  -I$HOME/sw/include foo.c -o foo  -L$HOME/sw/lib -lntl  -lm

If you are using GMP, then:

       % g++ -I$HOME/sw/include foo.c -o foo  -L$HOME/sw/lib -lntl -lgmp  -lm

If you are using GMP and `gf2x`, then

       % g++  -I$HOME/sw/include foo.c -o foo  -L$HOME/sw/lib -lntl -lgmp -lgf2x  -lm

## More Details

What follows is a more detailed description of the installation process.

Step 1. Extract the source files by executing:

       % gunzip ntl-xxx.tar.gz
       % tar xvf ntl-xxx.tar

Note that this will unpack everything into a sub-directory `ntl-xxx`, creating this directory if necessary. Next:

       % cd ntl-xxx
       % ls

You should see a file "`README`", and directories "`include`", "`doc`", and "`src`". The directory "`doc`" contains all the documentation. The file "`doc/tour.html`" contains a copy of the on-line documentation. The directory "`include`" contains all the header files within a subdirectory "`include/NTL`". The directory "`src`" contains everything else. Go there now:

       % cd src

Step 2. Run the configuration script.

Execute the command

       % ./configure [ variable=value ]...

This configure script generates the file "`makefile`" and the file "`../include/NTL/config.h`", based upon the values assigned to the variables on the command line.

Here are the most important variables, and their default values.

    CC=gcc               # The C compiler
    CXX=g++              # The C++ compiler
    CFLAGS=-O2           # C complilation flags
    CXXFLAGS=$(CFLAGS)   # C++ compilation flags (by default, same as CFLAGS)

    DEF_PREFIX=/usr/local # Default software directory
    PREFIX=$(DEF_PREFIX) # Directory in which to install NTL library components
    SHARED=off           # Generate a shared library (as well as static)

    NTL_STD_CXX=on       # ISO Mode switch

    NTL_GMP_LIP=off      # Switch to enable the use of GMP as primary
                         #   long integer package

    GMP_PREFIX=$(DEF_PREFIX) # Directory in which GMP components are installed

    NTL_GF2X_LIB=off     # Switch to enable the use of the gf2x package
                         #   for faster arithmetic over GF(2)[X]

    GF2X_PREFIX=$(DEF_PREFIX) # Directory in which gf2x components are installed

Examples.

- If you are happy with all the default values, run:

         % ./configure

  Actually, the initially installed `makefile` and `config.h` files already reflect the default values, and you do not have to even run the configure script.

- If your C/C++ compilers are called cc/CC, run:

         % ./configure CC=cc CXX=CC

- If you want to use, say, the options `-g` and `-O` for compiling `C` and `C++`, run:

         % ./configure "CFLAGS=-g -O"

  Note the use of quotes to keep the argument in one piece.

- If GMP (the GNU Multi-Precision package) is installed in a standard system directory, and you want to use it to obtain better performance for long integer arithemtic, run:

         % ./configure NTL_GMP_LIP=on

  If GMP was installed in `$HOME/sw`, run:

         % ./configure NTL_GMP_LIP=on GMP_PREFIX=$HOME/sw

  Go here for complete details.

- If `gf2x` is installed in a standard system directory, and you want to use it to obtain better performance for polynomial arithemtic over GF(2), run:

         % ./configure NTL_GF2X_LIB=on

  If `gf2x` was installed in `$HOME/sw`, run:

         % ./configure NTL_GF2X_LIB=on GF2X_PREFIX=$HOME/sw

  Go here for complete details.

- If you want to use traditional rather than ISO mode, run:

         % ./configure NTL_STD_CXX=off

- If you want to install NTL in the directory `$HOME/sw`, run:

         % ./configure PREFIX=$HOME/sw

There are a number of more esoteric configuration variables that can be set. See `config.txt` for a complete description.

Note that all of these configuration options can also be set by editing the two files `makefile` and `../include/NTL/def_config.h` by hand. These files are fairly simple and well documented, and so this is not too hard to do.

Note that the file "`../include/NTL/def_config.h`" contains a backup copy of the original `config.h` file, and that the file "`def_makefile`" contains a backup copy of the original `makefile` file.

This command is intended only as a convenience and -- more importantly -- to allow the configuration process to be script driven. This script does not perform any "magic", like finding out what the local C compiler is called, etc. If the defaults are not correct for your platform, you have to set an appropriate variable.

Step 3. Execute `make`.

Just type:

       % make

The build process after this point is fully automatic. But here is a description of what happens.

1. The makefile builds the file "`../include/NTL/mach_desc.h`", which defines some machine characteristics such as word size and machine precision. This is done by compiling and running a `C` program called `MakeDesc` that figures out these characteristics on its own, and prints some diagnostics to the terminal.

2. A script is run that "automagically" determines the best way to write a timing function on your platform. It tries different routines in the files `GetTime1.c`, `GetTime2.c`, etc., and when it finds a good one, it copies the file into `GetTime.c`.

3. The files "`lip_gmp_aux_impl.h`" and "`../include/NTL/gmp_aux.h`" are generated for use with GMP. If not using GMP, these files are still created, but they are empty.

4. The configuration wizard script is run. This script works in a sub-directory, compiling several programs, and performing a number of timing experiments, in order to determine the optimal setting for a number of flags in the file `../include/NTL/config.h`. When the script finishes (it may take several minutes), you will be told what the wizard thinks are the best settings, and your `config.h` file will be automatically updated. Note that any flags you set in Step 2 will be in effect while the wizard runs, and will be retained in the updated `config.h` file, with the exception of the flags

          NTL_LONG_LONG NTL_AVOID_FLOAT NTL_TBL_REM NTL_AVOID_BRANCHING
          NTL_SPMM_UL NTL_SPMM_ULL NTL_SPMM_ASM NTL_GF2X_NOINLINE NTL_GF2X_ALTCODE

   which are set by the wizard. Also note that if you do not want the wizard to run, you should pass `WIZARD=off` to the configure script; however, this is not recommended.

5. The makefile will compile all the source files, and then creates the library "`ntl.a`" in the current directory.

Note that for finer control you can optionally break up this process into the five component steps:

       % make setup1
       % make setup2
       % make setup3
       % make setup4
       % make ntl.a

After NTL is built.

Executing `make check` runs a series of timing and test programs. It is a good idea to run this to see if everything really went well.

Executing `make install` copies a number of files to a directory `<prefix>` that you specify by passing `PREFIX=<prefix>` as an argument to `configure` at configuration time, or as an argument to `make install` at installation time. The default is `/usr/local`, so either you need root permissions, or you choose a `<prefix>` for which you have write permission. The files `../include/NTL/*` are copied into `<prefix>/include/NTL`. The file `ntl.a` is copied to `<prefix>/lib/libntl.a`. The files `../doc/*` are copied into `<prefix>/share/doc/NTL`.

You can also "fine tune" the installation procedure further. See the configure documentation for details.

Executing `make uninstall` undoes `make install`.

Executing `make clobber` essentially undoes `make`. Make sure you do this if you re-build NTL for a different architecture!

Executing `make clean` will remove object files, but not `ntl.a`. To rebuild after executing `make clean`, execute `make ntl.a`.

Assuming you have installed NTL as above, to compile a program `foo.c` that uses NTL, execute

       g++  -I<prefix>/include foo.c -o foo  -L<prefix>/lib -lntl  -lm

This compiles `foo.c` as a `C++` program and creates the binary `foo`.

If you built NTL using GMP, execute:

       g++  -I<prefix>/include foo.c -o foo  -L<prefix>/lib -lntl  -L<gmp_prefix>/lib -lgmp  -lm

Of course, if `<prefix>` and `<gmp_prefix>` are the same, you do not need to duplicate the `-L` flags, and if either are standard directories, like `/usr/local`, you can leave out the corresponding `-I` and `-L` flags altogether.

Similarly, if you built NTL using `gf2x`, you should include flags

       -L<gf2x_prefix>/lib -lgf2x

on the command line.

This works even if you are not working in the directory in which you built NTL. If you are working in that directory, you can just execute

       make foo

## Building a Shared Library

By default, the above installation procedure builds a static library only. Static libraries are nice because the procedures for building and using them are nearly identical across various flavors of Unix. However, static libraries have their drawbacks, and sometimes it is desirable to build a shared library. This can be done (in theory) by simply passing `SHARED=on` to NTL's `configure`.

If you set `SHARED=on`, then behind the scenes, the procedure used by the `makefile` changes a bit. In particular, the magical GNU program `libtool` is used to deal with all idiosyncracies of shared libraries. You may need to set the configuration variable `LIBTOOL`, to point to another version of `libtool`. For example, on Mac OSX, the built-in command called `libtool` is not actually the GNU `libtool` program; in this case, you will want to set `LIBTOOL=glibtool`. On other systems, it may be necssary to download and install a fresh copy of the libtool program (which can be obtained from here). Note that if `SHARED=on`, then in addition to using the `libtool` program, the `makefile` relies on features specific to GNU make.

Note that if you want to build NTL as a shared library, then if you use them, GMP and `gf2x` must also be built and installed as shared libraries. Also note that to use a shared library version of NTL, you may have to do something special, like set a special shell variable: the output generated by the `libtool` program during `make install` should give specific instructions. In addition, if NTL is built as a shared library, then you typically do not have to include `-lgmp` (if using GMP), or `-lgf2x` (if using `gf2x`), or corresponding `-L` flags, or `-lm` on the command line when compiling programs that use NTL.

## 32-bit and 64-bit ABIs

An ABI (Application Binary Interface) defines the sizes of various `C` data types. Typically, with a 32-bit ABI, int's and long's are 32 bits, while on a 64-bit ABI, int's are 32 bits and long's are 64 bits. Some platforms support both 64-bit and 32-bit ABI's; typically in such settings, the 64-bit ABI will yield much better performance, while the 32-bit ABI is available for backward compatibility. In addition, the 64-bit ABI may not be the default: if you are using `gcc`, you need to pass the `-m64` flag to the compiler to get the 64-bit ABI.

When compiling NTL, you may want to try running `configure` with `CFLAGS="-O2 -m64"` to force a 64-bit ABI -- this may yield a very marked performance improvement.

If you are using NTL with either the GMP or `gf2x` libraries, then these must be built with the same ABI as NTL. The installation script for GMP will typically select the 64-bit ABI automatically if it is available. The installation script for `gf2x` may need some hints.

When compiling programs that use NTL, you must also ensure that the program is compiled with the same ABI as NTL. Again, if you want a 64-bit ABI, then just pass the flag `-m64` to the compiler.