aa9bc17601
BMakefiles and other bits will follow. Requested by: Andrey Chernov Made world by: Chuck Robey
138 lines
4.7 KiB
Plaintext
138 lines
4.7 KiB
Plaintext
THE GNU MP LIBRARY
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GNU MP is a library for arbitrary precision arithmetic, operating on signed
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integers, rational numbers, and floating point numbers. It has a rich set
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of functions, and the functions have a regular interface.
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GNU MP is designed to be as fast as possible, both for small operands and for
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huge operands. The speed is achieved by using fullwords as the basic
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arithmetic type, by using fast algorithms, by carefully optimized assembly
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code for the most common inner loops for a lots of CPUs, and by a general
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emphasis on speed (instead of simplicity or elegance).
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The speed of GNU MP is believed to be faster than any other similar library.
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The advantage for GNU MP increases with the operand sizes for certain
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operations, since GNU MP in many cases has asymptotically faster algorithms.
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GETTING STARTED
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First, you have to configure and compiler GNU MP. Simply typing
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./configure; make
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will normally do a reasonable job, but will not give optimal library
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execution speed. So unless you're very unpatient, please read the detailed
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instructions in the file INSTALL or in gmp.texi.
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Once you have compiled the library, you should write some small example, and
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make sure you can compile them. A typical compilation command is this:
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gcc -g your-file.c -I<gmp-source-dir> <gmp-bin-dir>libgmp.a -lm
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If you have installed the library, you can simply do:
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gcc -g your-file.c -lgmp -lm
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The -lm is normally not needed, since only a few functions in GNU MP use the
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math library.
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Here is a sample program that declares 2 variables, initializes them as
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required, and sets one of them from a signed integer, and the other from a
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string of digits. It then prints the product of the two numbers in base 10.
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#include <stdio.h>
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#include "gmp.h"
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main ()
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{
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mpz_t a, b, p;
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mpz_init (a); /* initialize variables */
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mpz_init (b);
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mpz_init (p);
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mpz_set_si (a, 756839); /* assign variables */
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mpz_set_str (b, "314159265358979323846", 0);
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mpz_mul (p, a, b); /* generate product */
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mpz_out_str (stdout, 10, p); /* print number without newline */
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puts (""); /* print newline */
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mpz_clear (a); /* clear out variables */
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mpz_clear (b);
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mpz_clear (p);
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exit (0);
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}
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This might look tedious, with all initializing and clearing. Fortunately
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some of these operations can be combined, and other operations can often be
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avoided. The example above would be written differently by an experienced
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GNU MP user:
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#include <stdio.h>
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#include "gmp.h"
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main ()
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{
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mpz_t b, p;
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mpz_init (p);
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mpz_init_set_str (b, "314159265358979323846", 0);
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mpz_mul_ui (p, b, 756839); /* generate product */
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mpz_out_str (stdout, 10, p); /* print number without newline */
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puts (""); /* print newline */
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exit (0);
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}
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OVERVIEW OF GNU MP
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There are five classes of functions in GNU MP.
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1. Signed integer arithmetic functions, mpz_*. These functions are intended
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to be easy to use, with their regular interface. The associated type is
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`mpz_t'.
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2. Rational arithmetic functions, mpq_*. For now, just a small set of
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functions necessary for basic rational arithmetics. The associated type
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is `mpq_t'.
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3. Floating-point arithmetic functions, mpf_*. If the C type `double'
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doesn't give enough precision for your application, declare your
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variables as `mpf_t' instead, set the precision to any number desired,
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and call the functions in the mpf class for the arithmetic operations.
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4. Positive-integer, hard-to-use, very low overhead functions are in the
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mpn_* class. No memory management is performed. The caller must ensure
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enough space is available for the results. The set of functions is not
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regular, nor is the calling interface. These functions accept input
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arguments in the form of pairs consisting of a pointer to the least
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significant word, and a integral size telling how many limbs (= words)
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the pointer points to.
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Almost all calculations, in the entire package, are made by calling these
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low-level functions.
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5. Berkeley MP compatible functions.
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To use these functions, include the file "mp.h". You can test if you are
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using the GNU version by testing if the symbol __GNU_MP__ is defined.
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For more information on how to use GNU MP, please refer to the documentation.
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It is composed from the file gmp.texi, and can be displayed on the screen or
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printed. How to do that, as well how to build the library, is described in
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the INSTALL file in this directory.
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REPORTING BUGS
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If you find a bug in the library, please make sure to tell us about it!
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Report bugs and propose modifications and enhancements to
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bug-gmp@prep.ai.mit.edu. What information is needed in a good bug report is
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described in the manual.
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