Re: Database madness
"Viktor T. Toth" <[email protected]> Sun, 26 Jul 2026 22:09:07 -0400
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Indeed it seems the pathology here is not about a hash table but about
how *NOBJECTS* itself grows for no good reason:
(%i1) eval_string_lisp("(list-length *NOBJECTS*)");
(%o1) [7]
(%i2) for i : 1 thru 10000 do is(f(x) > i);
(%o2) done
(%i3) eval_string_lisp("(list-length *NOBJECTS*)");
(%o3) [20007]
This is not kosher.
Viktor
On 2026-07-26 18:34, David Scherfgen via Maxima-discuss wrote:
> In this extreme case, maybe it's pathological. But comparisons happen
> all the time in the general simplifier, via sign, csign, mgrp, etc.,
> and in integration, limits, equation solving, ...
>
> Over a Maxima session, these number nodes accumulate irreversibly and
> keep slowing down Maxima more and more. Or maybe someone uses random
> numbers in expressions for some fancy algorithm, that would be the
> absolute "killer".
>
> Yes, Claude proposed a hash table. It can speed up some parts of this.
> Also, I think the database should only create nodes for numbers that
> actually appear in facts, and not as soon as they're used in a pure query.
>
> Raymond Toy <[email protected]> schrieb am Mo., 27. Juli 2026, 00:04:
>
> On 7/26/26 2:29 PM, David Scherfgen via Maxima-discuss wrote:
>
>> Hi all,
>>
>> Something funny to try:
>>
>> run_testsuite(tests=[rtest_limit_extra]);
>> for i : 1 thru 10000 do is(f(x) > i);
>> run_testsuite(tests=[rtest_limit_extra]);
>>
>> The second test run takes about 15 times as much time as the
>> first one.
>>
>> Why? Because when asking is(f(x) > i), a database node for the
>> number i is created (if there's none yet) in the variable
>> *NOBJECTS*. This slows down subsequent sign queries, because
>> Maxima has to search in a list that gets longer and longer.
> Kinda funny, but certainly a rather pathological case. This
> doesn’t seem like something anyone would do on purpose. (Maybe I
> lack imagination.)
>
> Could it be replaced by a hash table? I suppose that might break
> lots of code?
>
> ​
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<p>Indeed it seems the pathology here is not about a hash table but
about how *NOBJECTS* itself grows for no good reason:</p>
<p>(%i1) eval_string_lisp("(list-length *NOBJECTS*)");<br>
(%o1)=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0=
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0[7]<br>
(%i2) for i : 1 thru 10000 do is(f(x) > i);<br>
(%o2)=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0=
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 done<br>
(%i3) eval_string_lisp("(list-length *NOBJECTS*)");<br>
(%o3)=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0=
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0[20007]</p>
<p>This is not kosher.</p>
<p><br>
</p>
<p>Viktor</p>
<p><br>
</p>
<p><br>
</p>
<p><br>
</p>
<div class=3D"moz-cite-prefix">On 2026-07-26 18:34, David Scherfgen
via Maxima-discuss wrote:<br>
</div>
<blockquote type=3D"cite"
cite=3D"mid:[email protected]=
l.com">
<meta http-equiv=3D"content-type" content=3D"text/html; charset=3DU=
TF-8">
<div dir=3D"auto">In this extreme case, maybe it's pathological. Bu=
t
comparisons happen all the time in the general simplifier, via
sign, csign, mgrp, etc., and in integration, limits, equation
solving, ...
<div dir=3D"auto"><br>
</div>
<div dir=3D"auto">Over a Maxima session, these number nodes
accumulate irreversibly and keep slowing down Maxima more and
more. Or maybe someone uses random numbers in expressions for
some fancy algorithm, that would be the absolute "killer".</div=
>
<div dir=3D"auto">
<div dir=3D"auto"><br>
<div dir=3D"auto">Yes, Claude proposed a hash table. It can
speed up some parts of this. Also, I think the database
should only create nodes for numbers that actually appear
in facts, and not as soon as they're used in a pure query.<=
/div>
</div>
</div>
</div>
<br>
<div class=3D"gmail_quote gmail_quote_container">
<div dir=3D"ltr" class=3D"gmail_attr">Raymond Toy <<a
href=3D"mailto:[email protected]" moz-do-not-send=3D"true=
"
class=3D"moz-txt-link-freetext">[email protected]</a>>=
schrieb am Mo., 27. Juli 2026, 00:04:<br>
</div>
<blockquote class=3D"gmail_quote"
style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);=
padding-left:1ex">
<div>
<div>
<p style=3D"margin-bottom:19.2px;margin-top:0px">On 7/26/26=
2:29 PM, David Scherfgen via Maxima-discuss wrote:<br>
</p>
<blockquote type=3D"cite"
style=3D"border-color:rgb(119,119,119) rgb(119,119,119) rgb(119,119,119) =
rgb(114,159,207);border-left-width:2px;border-left-style:solid;color:rgb(=
119,119,119);column-rule-color:rgb(119,119,119);margin:19.2px 0px;outline=
-color:rgb(119,119,119);padding-left:16px;padding-right:16px;quotes:none;=
text-decoration-color:rgb(119,119,119);text-emphasis-color:rgb(119,119,11=
9)">
<div dir=3D"auto">Hi all,
<div dir=3D"auto"><br>
</div>
<div dir=3D"auto">Something funny to try:</div>
<div dir=3D"auto"><br>
</div>
<div dir=3D"auto">run_testsuite(tests=3D[rtest_limit_ex=
tra]);</div>
<div dir=3D"auto">for i : 1 thru 10000 do is(f(x) >
i);</div>
<div dir=3D"auto">run_testsuite(tests=3D[rtest_limit_ex=
tra]);</div>
<div dir=3D"auto"><br>
</div>
<div dir=3D"auto">The second test run takes about 15
times as much time as the first one.</div>
<div dir=3D"auto"><br>
</div>
<div dir=3D"auto">Why? Because when asking is(f(x) >=
i), a database node for the number i is created (if
there's none yet) in the variable *NOBJECTS*. This
slows down subsequent sign queries, because Maxima
has to search in a list that gets longer and longer.<=
/div>
</div>
</blockquote>
Kinda funny, but certainly a rather pathological case.
This doesn=E2=80=99t seem like something anyone would do on=
purpose. (Maybe I lack imagination.)
<p style=3D"margin-bottom:19.2px;margin-top:0px">Could it b=
e
replaced by a hash table? I suppose that might break
lots of code?</p>
</div>
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