<html><body><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; color: #000000"><div><br></div><div><br></div><hr id="zwchr" data-marker="__DIVIDER__"><div data-marker="__HEADERS__"><blockquote style="border-left:2px solid #1010FF;margin-left:5px;padding-left:5px;color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;"><b>From: </b>"Brian Goetz" <brian.goetz@oracle.com><br><b>To: </b>"Per-Ake Minborg" <per-ake.minborg@oracle.com>, "leyden-dev" <leyden-dev@openjdk.org><br><b>Sent: </b>Thursday, July 27, 2023 7:50:09 PM<br><b>Subject: </b>Re: Draft JEP Announcement: "Computed Constants"<br></blockquote></div><div><style style="display:none;">P {margin-top:0;margin-bottom:0;}</style></div><div data-marker="__QUOTED_TEXT__"><blockquote style="border-left:2px solid #1010FF;margin-left:5px;padding-left:5px;color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;"><font size="4"><font face="monospace">One thing that may not be
obvious about this work is that what it effectively does is
provide a supported, public, specified means to expose the
functionality that is now restricted to internal JDK use via
`@Stable`. (So computed constants is-to @Stable as VarHandles
are to Unsafe::{get,put}Xxx.)</font></font></blockquote><div><br></div><div>Not exactly, computed constant is more like an AtomicReference (as said in the javadoc) than a VarHandle.<span style="font-size: large;"><span style="font-family: monospace;"></span></span></div><div>For a computed constant stored in an instance field (of a non constant instance), you pay the indirection cost.</div><div><br data-mce-bogus="1"></div><div>Perhaps what is missing is a ComputedConstant that have a method get() that takes an instance as first parameter (like a VarHandle on an instance field does), so we can have one computed constant for all the instances, so no indirection once the code is optimized. <br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div>Rémi<br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><blockquote style="border-left:2px solid #1010FF;margin-left:5px;padding-left:5px;color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;"><br>
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<div class="moz-cite-prefix">On 7/27/2023 11:52 AM, Per-Ake Minborg
wrote:<br>
</div>
<blockquote cite="mid:DM6PR10MB42837B145AE7240575E9D057DA01A@DM6PR10MB4283.namprd10.prod.outlook.com">
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);" class="elementToProof">
<span class="x_elementToProof" style="font-size: 12pt; margin:
0px; background-color: rgb(255, 255, 255);"><span class="x_ContentPasted0 ContentPasted0" style="font-size:
14.6667px; margin: 0px; display: inline !important; color:
rgb(36, 36, 36); background-color: rgb(255, 255, 255);">Hi
all,</span></span></div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);" class="elementToProof">
<div class="x_elementToProof" style="font-size: 12pt; margin:
0px; background-color: rgb(255, 255, 255);">
<br class="x_ContentPasted0 ContentPasted0" style="font-size:
14.6667px; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);">
<span class="x_ContentPasted0 ContentPasted0" style="font-size: 14.6667px; margin: 0px; display: inline
!important; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);"> Maurizio and I have drafted a JEP for
computed constants, which are</span><br class="x_ContentPasted0 ContentPasted0" style="font-size:
14.6667px; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);">
<span class="x_ContentPasted0 ContentPasted0" style="font-size: 14.6667px; margin: 0px; display: inline
!important; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);"> immutable value holders that are
initialized at most once. They offer</span><br class="x_ContentPasted0 ContentPasted0" style="font-size:
14.6667px; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);">
<span class="x_ContentPasted0 ContentPasted0" style="font-size: 14.6667px; margin: 0px; display: inline
!important; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);"> the performance and safety benefits
of final fields while offering</span><br class="x_ContentPasted0 ContentPasted0" style="font-size:
14.6667px; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);">
<span class="x_ContentPasted0 ContentPasted0" style="font-size: 14.6667px; margin: 0px; display: inline
!important; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);"> greater flexibility as to the timing
of initialization. In the</span><br class="x_ContentPasted0
ContentPasted0" style="font-size: 14.6667px; color: rgb(36,
36, 36); background-color: rgb(255, 255, 255);">
<span class="x_ContentPasted0 ContentPasted0" style="font-size: 14.6667px; margin: 0px; display: inline
!important; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);"> context of Leyden, they could be one
basis for shifting computation</span><br class="x_ContentPasted0 ContentPasted0" style="font-size:
14.6667px; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);">
<span class="x_ContentPasted0 ContentPasted0" style="font-size: 14.6667px; margin: 0px; display: inline
!important; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);"> both forward and backward in time.</span><br class="x_ContentPasted0 ContentPasted0" style="font-size:
14.6667px; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);">
<br class="x_ContentPasted0 ContentPasted0" style="font-size:
14.6667px; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);">
</div>
<div class="x_elementToProof" style="font-size: 12pt; margin:
0px; background-color: rgb(255, 255, 255);">
<span class="x_ContentPasted0 ContentPasted0" style="font-size: 14.6667px; margin: 0px; display: inline
!important; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);"> The draft is here:</span><a href="https://openjdk.org/jeps/8312611" target="_blank" rel="noopener noreferrer" class="x_ContentPasted0 ContentPasted0
moz-txt-link-freetext" style="font-size: 14.6667px; margin:
0px; background-color: rgb(255, 255, 255);">https://openjdk.org/jeps/8312611</a><br class="x_ContentPasted0 ContentPasted0" style="font-size:
14.6667px; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);">
</div>
<div class="x_elementToProof" style="font-size: 12pt; margin:
0px; background-color: rgb(255, 255, 255);">
<br class="x_ContentPasted0 ContentPasted0" style="font-size:
14.6667px; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);">
<span class="x_ContentPasted0 ContentPasted0" style="font-size: 14.6667px; margin: 0px; display: inline
!important; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);"> Now that the Leyden repo is open,
I’ll publish the prototype code to a</span><br class="x_ContentPasted0 ContentPasted0" style="font-size:
14.6667px; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);">
<span class="x_ContentPasted0 ContentPasted0" style="font-size: 14.6667px; margin: 0px; display: inline
!important; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);"> new branch there shortly.</span><br class="x_ContentPasted0 ContentPasted0" style="font-size:
14.6667px; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);">
<br class="x_ContentPasted0 ContentPasted0" style="font-size:
14.6667px; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);">
</div>
<div class="x_elementToProof" style="font-size: 12pt; margin:
0px; background-color: rgb(255, 255, 255);">
<span class="x_ContentPasted0 ContentPasted0" style="font-size: 14.6667px; margin: 0px; display: inline
!important; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);"> Comments are welcome!</span><br class="x_ContentPasted0 ContentPasted0" style="font-size:
14.6667px; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);">
</div>
<div class="x_elementToProof" style="font-size: 12pt; margin:
0px; background-color: rgb(255, 255, 255);">
<br class="x_ContentPasted0 ContentPasted0" style="font-size:
14.6667px; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);">
<span class="x_ContentPasted0 ContentPasted0" style="font-size: 14.6667px; margin: 0px; display: inline
!important; color: rgb(36, 36, 36); background-color:
rgb(255, 255, 255);"> Best, Per</span></div>
<br>
</div>
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