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Some folks might think: “you still use RCS”?!? And we will say, hey, at least we switched from SCCS to RCS back in … I think it was around 1994 ... at least we are keeping up! :-) :-) :-) Logs say that SCCS version 18 became RCS version 19 on 1994 March 18. RCS served us well. But now it is time to move on. And so we are switching to git. Calc releases produce a lot of file changes. In the 125 releases of calc since 1996, when I started managing calc releases, there have been 15473 file mods!
107 lines
3.6 KiB
C
107 lines
3.6 KiB
C
/*
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* jump - trivial prime jump table
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*
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* Copyright (C) 1999-2007,2014 Landon Curt Noll
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*
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* Calc is open software; you can redistribute it and/or modify it under
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* the terms of the version 2.1 of the GNU Lesser General Public License
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* as published by the Free Software Foundation.
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*
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* Calc is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
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* Public License for more details.
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*
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* A copy of version 2.1 of the GNU Lesser General Public License is
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* distributed with calc under the filename COPYING-LGPL. You should have
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* received a copy with calc; if not, write to Free Software Foundation, Inc.
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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* Under source code control: 1994/06/29 04:03:55
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* File existed as early as: 1994
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*
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* chongo <was here> /\oo/\ http://www.isthe.com/chongo/
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* Share and enjoy! :-) http://www.isthe.com/chongo/tech/comp/calc/
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*/
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/*
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* If x is divisible by a trivial prime (2,3,5,7,11), then:
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*
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* x + jmpindx[ (x>>1)%JMPMOD ]
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*
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* is the value of the smallest value > x that is not divisible by a
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* trivial prime. JMPMOD is the product of the odd trivial primes.
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*
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* This table is useful for skipping values that are obviously not prime
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* by skipping values that are a multiple of trivial prime.
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*
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* If x is not divisible by a trivial prime, then:
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*
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* x + jmp[ -jmpindx[(x>>1)%JMPMOD] ]
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*
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* is the value of the smallest value > x that is not divisible by a
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* trivial prime.
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*
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* If jmpindx[y] > 0 (y = x mod JMPMOD*2), then it refers to an 'x' that
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* is divisible by a trivial prime and jmpindx[y] is the offset to the next
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* value that is not divisible.
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*
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* If jmpindx[y] <= 0, then 'x' is not divisible by a trivial prime and
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* the negative of jmpindx[y] is the index into the jmp[] table. We use
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* successive values from jmp[] (wrapping around to the beginning when
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* we move off the end of jmp[]) to move to higher and higher values
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* that are not divisible by trivial primes.
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*
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* Instead of testing successive odd values, this system allows us to
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* skip odd values divisible by trivial primes. This is process on the
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* average reduces the values we need to test by a factor of at least 2.4.
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*/
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#if !defined(INCLUDE_JUMP_H)
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#define INCLUDE_JUMP_H
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#if defined(CALC_SRC) /* if we are building from the calc source tree */
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# include "have_const.h"
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# include "decl.h"
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#else
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# include <calc/have_const.h>
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# include <calc/decl.h>
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#endif
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/*
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* trivial prime CONSTants
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*/
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#define JMPMOD (3*5*7*11) /* product of odd trivial primes */
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#define JMPSIZE (2*4*6*10) /* ints mod JMPMOD not div by trivial primes */
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#define JPRIME (prime+4) /* pointer to first non-trivial prime */
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/* given x, return the index within jmpindx that applies */
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#define jmpmod(x) (((x)>>1)%JMPMOD)
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/* jmpindx table value */
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#define jmpindxval(x) (jmpindx[jmpmod(x)])
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/* return the smallest value >= x not divisible by a trivial prime */
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#define firstjmp(x,tmp) ((tmp) = jmpindxval(x), ((tmp) > 0) ? ((x)+(tmp)) : (x))
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/* given x not divisible by a trivial prime, return jmp[] index */
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#define jmpptr(x) (-jmpindxval(x))
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/* given a jmp pointer, return current jump increment and bump the pointer */
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#define nxtjmp(p) ( *( ((p)<lastjmp) ? ((p)++) : (((p)=jmp),lastjmp) ) )
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/* given a jmp pointer, return dec pointer and return previous jump increment */
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#define prevjmp(p) ( *( ((p)>jmp) ? (--(p)) : ((p)=lastjmp) ) )
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/*
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* external jump tables
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*/
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EXTERN CONST short jmpindx[];
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EXTERN CONST unsigned char jmp[];
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EXTERN CONST unsigned char *CONST lastjmp;
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#endif /* !INCLUDE_JUMP_H */
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