[M3devel] LONGINT problem?

Fri Jul 15 23:53:36 CEST 2011

I just checekd, and I can confirm that the LONGINT version of the code
produces INCORRECT results on a 32 bit system, as well as a 64 bit system.
 Both are running Linux, with cm3 5.8.6

On Thu, Jul 14, 2011 at 8:30 PM, Daniel Alejandro Benavides D. <
dabenavidesd at yahoo.es> wrote:

> Hi all:
> the problem as I see is that your program isn't typed for any platform in
> specific just to give you the best answer, then I would stick to the
> original and track down the source of the problem (this is very point of
> type checking, and e.g extended static checking if I may say so, the need to
> verify your statements, the other approach is too cumbersome, i.e make it
> believe it works when it doesn't). IMHO this a symptom of UNSAFE type
> checking problem, rather of programming or programmer error.
> I hope to be clarified about this, as far as I know LONGINT isn't INTEGER
> but a bigger or equal type (a bigger INTEGER) which translates better to be
> a super type, since it isn't I wonder why is that needed a different type
> checker for that (we can transform INTEGER to be the true super type and
> LONGINT to be a subtype), can't we make the same checking and just range
> check everything else (so it doesn't bother to rewrite every platform code,
> a bad symptom certainly, yet I approve the change in the language SPEC but
> not its type checking).
> Thanks in advance
>
> --- El *jue, 14/7/11, Coleburn, Randy <rcolebur at SCIRES.COM>* escribió:
>
>
> De: Coleburn, Randy <rcolebur at SCIRES.COM>
> Asunto: Re: [M3devel] LONGINT problem?
> Para: "m3devel" <m3devel at elegosoft.com>, "Ken Durocher" <
> kcdurocher at gmail.com>
> Fecha: jueves, 14 de julio, 2011 18:15
>
>
> Ken:
>
>
>
> On what platform (OS and CPU) are you building and running your Modula-3
> program?
>
>
>
> Support for LONGINT is a relatively new addition to CM3, so it is possible
> that something is broken.  Perhaps your program can help us track it down.
>
>
>
> I haven’t checked thru your program yet, but the fact that it gives the
> right answer using INTEGER, but not when using LONGINT, seems to point to
> the LONGINT implementation as a potential problem source we should
> investigate.
>
>
>
> Regards,
>
> Randy Coleburn
>
>
>
> *From:* Ken Durocher [mailto:kcdurocher at gmail.com]
> *Sent:* Thursday, July 14, 2011 7:00 PM
> *To:* Jay K
> *Cc:* m3devel
> *Subject:* Re: [M3devel] LONGINT problem?
>
>
>
> Sorry, to clarify, the LONGINT code does NOT give the correct output, but
> the INTEGER code DOES.
>
>
>
> I did not write this C code, but it's output is the same as all the other
> examples (there is a Java example too, if you want that):
>
>
>
> #include <stdio.h>
>
> #include <stdlib.h>
>
> #include <stdint.h>
>
>
>
> /* should be 64-bit integers if going over 1 billion */
>
> typedef unsigned long xint;
>
> #define FMT "%lu"
>
>
>
> xint total, prim, max_peri;
>
> xint U[][9] =  {{ 1, -2, 2,  2, -1, 2,  2, -2, 3},
>
>                         { 1,  2, 2,  2,  1, 2,  2,  2, 3},
>
>                         {-1,  2, 2, -2,  1, 2, -2,  2, 3}};
>
>
>
> void new_tri(xint in[])
>
> {
>
>             int i;
>
>             xint t[3], p = in[0] + in[1] + in[2];
>
>
>
>             if (p > max_peri) return;
>
>
>
>             prim ++;
>
>
>
>             /* for every primitive triangle, its multiples would be
> right-angled too;
>
>             * count them up to the max perimeter */
>
>             total += max_peri / p;
>
>
>
>             /* recursively produce next tier by multiplying the matrices
> */
>
>             for (i = 0; i < 3; i++) {
>
>                         t[0] = U[i][0] * in[0] + U[i][1] * in[1] + U[i][2]
> * in[2];
>
>                         t[1] = U[i][3] * in[0] + U[i][4] * in[1] + U[i][5]
> * in[2];
>
>                         t[2] = U[i][6] * in[0] + U[i][7] * in[1] + U[i][8]
> * in[2];
>
>                         new_tri(t);
>
>             }
>
> }
>
>
>
> int main()
>
> {
>
>             xint seed[3] = {3, 4, 5};
>
>
>
>             for (max_peri = 10; max_peri <= 100000000; max_peri *= 10) {
>
>                         total = prim = 0;
>
>                         new_tri(seed);
>
>
>
>                         printf(  "Up to "FMT": "FMT" triples, "FMT"
> primitives.\n",
>
>                                     max_peri, total, prim);
>
>             }
>
>             return 0;
>
> }
>
>
>
> The output from that code is:
>
>
>
> Up to 10: 0 triples, 0 primitives.
>
> Up to 100: 17 triples, 7 primitives.
>
> Up to 1000: 325 triples, 70 primitives.
>
> Up to 10000: 4858 triples, 703 primitives.
>
> Up to 100000: 64741 triples, 7026 primitives.
>
> Up to 1000000: 808950 triples, 70229 primitives.
>
> Up to 10000000: 9706567 triples, 702309 primitives.
>
> Up to 100000000: 113236940 triples, 7023027 primitives.
>
>
>
> Note this output corresponds with the INTEGER output.
>
>
>
> On Thu, Jul 14, 2011 at 5:17 PM, Jay K <jay.krell at cornell.edu<http://mc/compose?to=jay.krell@cornell.edu>>
> wrote:
>
> Can you isolate if the problem is the formating/printing, or if it is in
> the computation?
> i.e.:
>
> Use "unsafe" and print out a little hex dump of the integer/longint
> variables?
>
> As well, what does LONGINT on a 64bit machine do? Eh..well, it might work,
> it might not.
> Doesn't really matter. Let's focus on non-working 32bit machine with
> LONGINT.
>
> Also, please confirm which is the right, i.e. by writing it in C.
> Also, maybe just try to format as unsigned/hex using the safe interfaces?
> Also, this will be good to add to our automated tests. Assuming it doesn't
> run too slowly.
> Assuming it reproduces for anyone else (sorry, a bit rude of me).
>
> Later, thank you,
>  - Jay
>
> ------------------------------
>
> Date: Thu, 14 Jul 2011 16:26:05 -0500
> From: kcdurocher at gmail.com <http://mc/compose?to=kcdurocher@gmail.com>
> To: m3devel at elegosoft.com <http://mc/compose?to=m3devel@elegosoft.com>
> Subject: [M3devel] LONGINT problem?
>
>
>
> I was writing a program to calculate "Pythagorean triples" recursively, and
> ran into a problem.  Here's the program:
>
>
>
> MODULE PyTriples EXPORTS Main;
>
>
>
> IMPORT IO, Fmt;
>
>
>
> VAR tcnt, pcnt, max, i: LONGINT;
>
>
>
> PROCEDURE NewTriangle(a, b, c: LONGINT; VAR tcount, pcount: LONGINT) =
>
>   VAR perim := a + b + c;
>
>   BEGIN
>
>     IF perim <= max THEN
>
>       pcount := pcount + 1L;
>
>       tcount := tcount + max DIV perim;
>
>       NewTriangle(a-2L*b+2L*c, 2L*a-b+2L*c, 2L*a-2L*b+3L*c, tcount,
> pcount);
>
>       NewTriangle(a+2L*b+2L*c, 2L*a+b+2L*c, 2L*a+2L*b+3L*c, tcount,
> pcount);
>
>       NewTriangle(2L*b+2L*c-a, b+2L*c-2L*a, 2L*b+3L*c-2L*a, tcount,
> pcount);
>
>     END;
>
>   END NewTriangle;
>
>
>
> BEGIN
>
> i := 100L;
>
>
>
> REPEAT
>
>   max := i;
>
>   tcnt := 0L;
>
>   pcnt := 0L;
>
>   NewTriangle(3L, 4L, 5L, tcnt, pcnt);
>
>   IO.Put(Fmt.LongInt(i) & ": " & Fmt.LongInt(tcnt) & " Triples, " &
>
>     Fmt.LongInt(pcnt) & " Primitives\n");
>
>   i := i * 10L;
>
> UNTIL i = 10000000L;
>
>
>
> END PyTriples.
>
>
>
> This outputs:
>
>
>
> 100: 17 Triples, 7 Primitives
>
> 1000: 325 Triples, 70 Primitives
>
> 10000: 0858 Triples, 703 Primitives
>
> 100000: 40701 Triples, 7024 Primitives
>
> 1000000: 808950 Triples, 70229 Primitives
>
>
>
> However, if I just use INTEGER on a 64 bit machine, I get the proper
> output:
>
>
>
> 100: 17 Triples, 7 Primitives
>
> 1000: 325 Triples, 70 Primitives
>
> 10000: 4858 Triples, 703 Primitives
>
> 100000: 64741 Triples, 7026 Primitives
>
> 1000000: 808950 Triples, 70229 Primitives
>
>
>
> Note how 10000 and 100000 are different. The code is literally exactly the
> same, only with LONGINT replaced by INTEGER.
>
>
>
>
>
>
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