mirror of https://github.com/python/cpython
ec766a6179
Resizing is used _inside_ libmpdec functions, and it is permitted to change x->alloc several times while setting x->len at the end of the function. Therefore, for dynamic mpd_t x->alloc can _temporarily_ drop below x->len. Of course the final result always has x->len <= x->alloc. For static mpd_t this cannot happen, since resizing to a smaller coefficient is a no-op. 2) Remove micro optimization in mpd_switch_to_dyn(): Previously only the valid initialized part of the existing coefficient up to x->len was copied to the new dynamic memory area. Now copying does the same as realloc() and the entire old memory area is copied. The rationale for this change is that it is no longer needed to memorize the explanation given in 1). |
||
|---|---|---|
| .. | ||
| literature | ||
| README.txt | ||
| basearith.c | ||
| basearith.h | ||
| bits.h | ||
| constants.c | ||
| constants.h | ||
| context.c | ||
| convolute.c | ||
| convolute.h | ||
| crt.c | ||
| crt.h | ||
| difradix2.c | ||
| difradix2.h | ||
| fnt.c | ||
| fnt.h | ||
| fourstep.c | ||
| fourstep.h | ||
| io.c | ||
| io.h | ||
| memory.c | ||
| memory.h | ||
| mpdecimal.c | ||
| mpdecimal.h | ||
| numbertheory.c | ||
| numbertheory.h | ||
| sixstep.c | ||
| sixstep.h | ||
| transpose.c | ||
| transpose.h | ||
| typearith.h | ||
| umodarith.h | ||
| vccompat.h | ||
| vcdiv64.asm | ||
| vcstdint.h | ||
README.txt
libmpdec
========
libmpdec is a fast C/C++ library for correctly-rounded arbitrary precision
decimal floating point arithmetic. It is a complete implementation of
Mike Cowlishaw/IBM's General Decimal Arithmetic Specification.
Files required for the Python _decimal module
=============================================
Core files for small and medium precision arithmetic
----------------------------------------------------
basearith.{c,h} -> Core arithmetic in base 10**9 or 10**19.
bits.h -> Portable detection of least/most significant one-bit.
constants.{c,h} -> Constants that are used in multiple files.
context.c -> Context functions.
io.{c,h} -> Conversions between mpd_t and ASCII strings,
mpd_t formatting (allows UTF-8 fill character).
memory.{c,h} -> Allocation handlers with overflow detection
and functions for switching between static
and dynamic mpd_t.
mpdecimal.{c,h} -> All (quiet) functions of the specification.
typearith.h -> Fast primitives for double word multiplication,
division etc.
Visual Studio only:
~~~~~~~~~~~~~~~~~~~
vccompat.h -> snprintf <==> sprintf_s and similar things.
vcstdint.h -> stdint.h (included in VS 2010 but not in VS 2008).
vcdiv64.asm -> Double word division used in typearith.h. VS 2008 does
not allow inline asm for x64. Also, it does not provide
an intrinsic for double word division.
Files for bignum arithmetic:
----------------------------
The following files implement the Fast Number Theoretic Transform
used for multiplying coefficients with more than 1024 words (see
mpdecimal.c: _mpd_fntmul()).
umodarith.h -> Fast low level routines for unsigned modular arithmetic.
numbertheory.{c,h} -> Routines for setting up the Number Theoretic Transform.
difradix2.{c,h} -> Decimation in frequency transform, used as the
"base case" by the following three files:
fnt.{c,h} -> Transform arrays up to 4096 words.
sixstep.{c,h} -> Transform larger arrays of length 2**n.
fourstep.{c,h} -> Transform larger arrays of length 3 * 2**n.
convolute.{c,h} -> Fast convolution using one of the three transform
functions.
transpose.{c,h} -> Transpositions needed for the sixstep algorithm.
crt.{c,h} -> Chinese Remainder Theorem: use information from three
transforms modulo three different primes to get the
final result.
Pointers to literature, proofs and more
=======================================
literature/
-----------
REFERENCES.txt -> List of relevant papers.
bignum.txt -> Explanation of the Fast Number Theoretic Transform (FNT).
fnt.py -> Verify constants used in the FNT; Python demo for the
O(N**2) discrete transform.
matrix-transform.txt -> Proof for the Matrix Fourier Transform used in
fourstep.c.
six-step.txt -> Show that the algorithm used in sixstep.c is
a variant of the Matrix Fourier Transform.
mulmod-64.txt -> Proof for the mulmod64 algorithm from
umodarith.h.
mulmod-ppro.txt -> Proof for the x87 FPU modular multiplication
from umodarith.h.
umodarith.lisp -> ACL2 proofs for many functions from umodarith.h.
Library Author
==============
Stefan Krah <skrah@bytereef.org>