<html><head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body>
<p><br>
</p>
<div class="moz-cite-prefix">On 28/07/2023 10:23, Glavo wrote:<br>
</div>
<blockquote type="cite" cite="mid:CAJL5A3=if3JKGDF9RD5LX9CKrPd5QpsXuoeKCfWL3V1vSsBAgA@mail.gmail.com">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<blockquote class="gmail_quote" style="margin:0px
0px 0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex"><span style="color:rgb(0,0,0);font-family:Calibri,Arial,Helvetica,sans-serif;font-size:16px">I
share your view that it is important to be
able to use ComputedConstant "early" in the VM
startup sequence. There is nothing inherent to
the proposed API that *requires* a lambda or a
method reference to be used. An anonymous or
regular class, implementing Supplier would
also do. Also, there is nothing fundamental
that prevents us from *implementing* the API
in a way it can be used "early".</span><br>
</blockquote>
<div dir="ltr"><br>
</div>
<div dir="ltr">If anonymous classes need to be
used, what is its advantage over the
initialization-on-demand holder idiom?</div>
<div dir="ltr">It seems to be completely inferior
to initialization-on-demand holder idiom, except
for being able to use it as instance fields.<br>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</blockquote>
<p>Note that, using a ComputedConstant _list_ you can have a single
supplier to serve a big number of computed constants. This is
something that the holder idiom cannot do (and IMHO, _the_ most
useful thing provided by the API).</p>
<p>To make a concrete example - jextract generates classes with lots
of constants (MethodHandles, VarHandles and MemoryLayouts).</p>
<p>To make startup acceptable, we have to "aplit" the constants into
several holder class.</p>
<p>When extracting sizeable libraries, it is common to have hundreds
of such holder classes. So, peak performance and startup comes at
a footprint cost.</p>
<p>We have made an experiment to tweak jextract generation to use a
list of computed constants instead with a _single_ supplier. The
index passed to the list is the index of the constant jextract
wants to retrieve (basically think of this as a dynamic constant
pool implementation).</p>
<p>This gives better startup that with the split holder idiom we use
today, same peak performance (because all constants are still
treated as such by C2, even if initialized lazily) and gneerates
_one_ class instead of hundreds.</p>
<p>Maurizio<br>
</p>
<blockquote type="cite" cite="mid:CAJL5A3=if3JKGDF9RD5LX9CKrPd5QpsXuoeKCfWL3V1vSsBAgA@mail.gmail.com">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr"><br>
</div>
<div>Glavo</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Fri, Jul 28, 2023 at
3:29 PM Per-Ake Minborg <<a href="mailto:per-ake.minborg@oracle.com" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">per-ake.minborg@oracle.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>
<div dir="ltr">
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">Hi
Rémi,<br>
<br>
I share your view that it is important to be able to use
ComputedConstant "early" in the VM startup sequence.
There is nothing inherent to the proposed API that
*requires* a lambda or a method reference to be used. An
anonymous or regular class, implementing Supplier would
also do. Also, there is nothing fundamental that
prevents us from *implementing* the API in a way it can
be used "early".<br>
<br>
We do not add any keywords, the JEP is a pure library
approach so, I do not foresee any backward compatibility
issues.</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">Thanks
for your feedback.</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">Best,
Per</div>
<hr style="display:inline-block;width:98%">
<div id="m_-1284864079631678419m_-4333802865184303049divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" face="Calibri,
sans-serif" color="#000000"><b>From:</b> <a href="mailto:forax@univ-mlv.fr" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">forax@univ-mlv.fr</a>
<<a href="mailto:forax@univ-mlv.fr" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">forax@univ-mlv.fr</a>><br>
<b>Sent:</b> Thursday, July 27, 2023 6:36 PM<br>
<b>To:</b> Maurizio Cimadamore <<a href="mailto:maurizio.cimadamore@oracle.com" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">maurizio.cimadamore@oracle.com</a>><br>
<b>Cc:</b> Per-Ake Minborg <<a href="mailto:per-ake.minborg@oracle.com" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">per-ake.minborg@oracle.com</a>>;
leyden-dev <<a href="mailto:leyden-dev@openjdk.org" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">leyden-dev@openjdk.org</a>>;
John Rose <<a href="mailto:john.r.rose@oracle.com" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">john.r.rose@oracle.com</a>><br>
<b>Subject:</b> [External] : Re: Draft JEP
Announcement: "Computed Constants"</font>
<div> </div>
</div>
<div>
<div style="font-family:arial,helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">
<div><br>
</div>
<div><br>
</div>
<hr id="m_-1284864079631678419m_-4333802865184303049x_zwchr">
<div>
<blockquote style="border-left:2px solid
rgb(16,16,255);margin-left:5px;padding-left:5px;color:rgb(0,0,0);font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt"><b>From:
</b>"Maurizio Cimadamore" <<a href="mailto:maurizio.cimadamore@oracle.com" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">maurizio.cimadamore@oracle.com</a>><br>
<b>To: </b>"Remi Forax" <<a href="mailto:forax@univ-mlv.fr" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">forax@univ-mlv.fr</a>>,
"Per-Ake Minborg" <<a href="mailto:per-ake.minborg@oracle.com" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">per-ake.minborg@oracle.com</a>><br>
<b>Cc: </b>"leyden-dev" <<a href="mailto:leyden-dev@openjdk.org" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">leyden-dev@openjdk.org</a>>,
"John Rose" <<a href="mailto:john.r.rose@oracle.com" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">john.r.rose@oracle.com</a>><br>
<b>Sent: </b>Thursday, July 27, 2023 6:14:48 PM<br>
<b>Subject: </b>Re: Draft JEP Announcement:
"Computed Constants"<br>
</blockquote>
</div>
<div>
<blockquote style="border-left:2px solid
rgb(16,16,255);margin-left:5px;padding-left:5px;color:rgb(0,0,0);font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt">
<p>Hi Remi<br>
Yes, of course we were aware of that.<br>
<br>
Think of this proposal as an API-driven approach
(in the style of ThreadLocal, ClassValue,
ScopedValue, ...) which delivers more or less
the same feature, but w/o changing the language.</p>
<p><br>
</p>
<p>One thing that's attractive about the API
approach is that it is not limited to just
static fields, but it can also work for instance
fields as well.</p>
<p><br>
</p>
<p>(that said, I agree the two jeps should somehow
be related/link to each other)</p>
</blockquote>
<div><br>
</div>
<div>I see two problems with your suggested
approach:<br>
</div>
<div>- this proposal is on top of lambdas, which
means that it can be used for applications but not
for the VM startup because it can only be used
after method handles sub-system have been
initialized.</div>
<div>- this is not a backward compatible change, if
you add a new keyword to static final fields, you
can rewrite any public static final fields to a
public lazy static final field,</div>
<div> by example, String.CASE_INSENSITIVE_ORDER
which is rarely used but can not be changed with
your proposal.</div>
<div><br>
</div>
<blockquote style="border-left:2px solid
rgb(16,16,255);margin-left:5px;padding-left:5px;color:rgb(0,0,0);font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt">
<p><br>
Maurizio</p>
</blockquote>
<div><br>
</div>
<div>Rémi<br>
</div>
<div><br>
</div>
<blockquote style="border-left:2px solid
rgb(16,16,255);margin-left:5px;padding-left:5px;color:rgb(0,0,0);font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt">
<p><br>
</p>
<div>On 27/07/2023 17:09, Remi Forax wrote:<br>
</div>
<blockquote>
<div style="font-family:arial,helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">
<div>Hello,<br>
</div>
<div>Are you aware of the lazy static final
fields proposal ?<br>
</div>
<div> <a href="https://bugs.openjdk.org/browse/JDK-8209964" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">
https://bugs.openjdk.org/browse/JDK-8209964</a><br>
</div>
<div><br>
</div>
<div>In think both proposals should be merged.<br>
</div>
<div><br>
</div>
<div>Rémi<br>
</div>
<div><br>
</div>
<hr id="m_-1284864079631678419m_-4333802865184303049x_zwchr">
<div>
<blockquote style="border-left:2px solid
rgb(16,16,255);margin-left:5px;padding-left:5px;color:rgb(0,0,0);font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt"><b>From:
</b>"Per-Ake Minborg" <a href="mailto:per-ake.minborg@oracle.com" target="_blank" moz-do-not-send="true">
<per-ake.minborg@oracle.com></a><br>
<b>To: </b>"leyden-dev" <a href="mailto:leyden-dev@openjdk.org" target="_blank" moz-do-not-send="true">
<leyden-dev@openjdk.org></a><br>
<b>Sent: </b>Thursday, July 27, 2023
5:52:46 PM<br>
<b>Subject: </b>Draft JEP Announcement:
"Computed Constants"<br>
</blockquote>
</div>
<div>
<blockquote style="border-left:2px solid
rgb(16,16,255);margin-left:5px;padding-left:5px;color:rgb(0,0,0);font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt">
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-size:12pt;margin:0px;background-color:rgb(255,255,255)"><span style="font-size:14.6667px;margin:0px;color:rgb(36,36,36);background-color:rgb(255,255,255);display:inline">Hi
all,</span></span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">
<div style="font-size:12pt;margin:0px;background-color:rgb(255,255,255)">
<br style="font-size:14.6667px;color:rgb(36,36,36);background-color:rgb(255,255,255)">
<span style="font-size:14.6667px;margin:0px;color:rgb(36,36,36);background-color:rgb(255,255,255);display:inline">
Maurizio and I have drafted a JEP
for computed constants, which are</span><br style="font-size:14.6667px;color:rgb(36,36,36);background-color:rgb(255,255,255)">
<span style="font-size:14.6667px;margin:0px;color:rgb(36,36,36);background-color:rgb(255,255,255);display:inline">
immutable value holders that are
initialized at most once. They
offer</span><br style="font-size:14.6667px;color:rgb(36,36,36);background-color:rgb(255,255,255)">
<span style="font-size:14.6667px;margin:0px;color:rgb(36,36,36);background-color:rgb(255,255,255);display:inline">
the performance and safety benefits
of final fields while offering</span><br style="font-size:14.6667px;color:rgb(36,36,36);background-color:rgb(255,255,255)">
<span style="font-size:14.6667px;margin:0px;color:rgb(36,36,36);background-color:rgb(255,255,255);display:inline">
greater flexibility as to the timing
of initialization. In the</span><br style="font-size:14.6667px;color:rgb(36,36,36);background-color:rgb(255,255,255)">
<span style="font-size:14.6667px;margin:0px;color:rgb(36,36,36);background-color:rgb(255,255,255);display:inline">
context of Leyden, they could be one
basis for shifting computation</span><br style="font-size:14.6667px;color:rgb(36,36,36);background-color:rgb(255,255,255)">
<span style="font-size:14.6667px;margin:0px;color:rgb(36,36,36);background-color:rgb(255,255,255);display:inline">
both forward and backward in time.</span><br style="font-size:14.6667px;color:rgb(36,36,36);background-color:rgb(255,255,255)">
<br style="font-size:14.6667px;color:rgb(36,36,36);background-color:rgb(255,255,255)">
</div>
<div style="font-size:12pt;margin:0px;background-color:rgb(255,255,255)">
<span style="font-size:14.6667px;margin:0px;color:rgb(36,36,36);background-color:rgb(255,255,255);display:inline">
The draft is here:</span><a href="https://openjdk.org/jeps/8312611" rel="noopener noreferrer" style="font-size:14.6667px;margin:0px;background-color:rgb(255,255,255)" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">https://openjdk.org/jeps/8312611</a><br style="font-size:14.6667px;color:rgb(36,36,36);background-color:rgb(255,255,255)">
</div>
<div style="font-size:12pt;margin:0px;background-color:rgb(255,255,255)">
<br style="font-size:14.6667px;color:rgb(36,36,36);background-color:rgb(255,255,255)">
<span style="font-size:14.6667px;margin:0px;color:rgb(36,36,36);background-color:rgb(255,255,255);display:inline">
Now that the Leyden repo is open,
I’ll publish the prototype code to a</span><br style="font-size:14.6667px;color:rgb(36,36,36);background-color:rgb(255,255,255)">
<span style="font-size:14.6667px;margin:0px;color:rgb(36,36,36);background-color:rgb(255,255,255);display:inline">
new branch there shortly.</span><br style="font-size:14.6667px;color:rgb(36,36,36);background-color:rgb(255,255,255)">
<br style="font-size:14.6667px;color:rgb(36,36,36);background-color:rgb(255,255,255)">
</div>
<div style="font-size:12pt;margin:0px;background-color:rgb(255,255,255)">
<span style="font-size:14.6667px;margin:0px;color:rgb(36,36,36);background-color:rgb(255,255,255);display:inline">
Comments are welcome!</span><br style="font-size:14.6667px;color:rgb(36,36,36);background-color:rgb(255,255,255)">
</div>
<div style="font-size:12pt;margin:0px;background-color:rgb(255,255,255)">
<br style="font-size:14.6667px;color:rgb(36,36,36);background-color:rgb(255,255,255)">
<span style="font-size:14.6667px;margin:0px;color:rgb(36,36,36);background-color:rgb(255,255,255);display:inline">
Best, Per</span></div>
<br>
</div>
<br>
</blockquote>
</div>
</div>
</blockquote>
<br>
</blockquote>
</div>
</div>
</div>
</div>
</div>
</blockquote>
</div>
</blockquote>
</body>
</html>