<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:"Intel Clear";
panose-1:2 11 6 4 2 2 3 2 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman",serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-reply;
font-family:"Intel Clear",sans-serif;
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;
font-family:"Calibri",sans-serif;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang="EN-US" link="blue" vlink="purple">
<div class="WordSection1">
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Intel Clear",sans-serif;color:#1F497D">Simple strides are a fairly specific use case that apply to dense matrices and regular problems. I am not denying that those problems exist, but they are
a subset. As I understand it, regular applications are a shrinking fraction of the application domain.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Intel Clear",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Intel Clear",sans-serif;color:#1F497D">Does any current hardware support strides natively? If not, maybe we have a little time to work out that interface.<o:p></o:p></span></p>
<p class="MsoNormal"><a name="_MailEndCompose"><span style="font-size:11.0pt;font-family:"Intel Clear",sans-serif;color:#1F497D"><o:p> </o:p></span></a></p>
<div style="border:none;border-left:solid blue 1.5pt;padding:0in 0in 0in 4.0pt">
<div>
<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Jeff Hammond [mailto:jeff.science@gmail.com]
<br>
<b>Sent:</b> Thursday, October 29, 2015 3:09 PM<br>
<b>To:</b> Underwood, Keith D <keith.d.underwood@intel.com><br>
<b>Cc:</b> Hefty, Sean <sean.hefty@intel.com>; Howard Pritchard <hppritcha@gmail.com>; ofiwg@lists.openfabrics.org<br>
<b>Subject:</b> Re: [ofiwg] strided IOVs<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal">Both GA/ARMCI and SHMEM utilize regular aka simple strided operations in RMA. GA_Acc/ARMCI_AccS/MPI_Accumulate map to fi_atomic, that means those also need to support strided, assuming RMA does.<o:p></o:p></p>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">I think only simple strided is worth supporting, because it is O(1) metadata. General gather/scatter ala iovec is unlikely to optimizable relative to a higher-level software implementation, so I don't see a good reason to put it into OFI.<o:p></o:p></p>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">Jeff<o:p></o:p></p>
</div>
</div>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal">On Thu, Oct 29, 2015 at 4:46 AM, Underwood, Keith D <<a href="mailto:keith.d.underwood@intel.com" target="_blank">keith.d.underwood@intel.com</a>> wrote:<o:p></o:p></p>
<blockquote style="border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in">
<p class="MsoNormal">Exactly. However, we should be careful about what we are adding here. A strided interface is a very specific special case that applies to regular problems. There is a bready of MPI derived datatype capabilities that are not covered by
a simple stride. What are the objectives for covering datatypes? Is the IOVEC interface the right place to glue in the first handling of a special case of datatypes?<o:p></o:p></p>
<div>
<div>
<p class="MsoNormal"><br>
> -----Original Message-----<br>
> From: <a href="mailto:ofiwg-bounces@lists.openfabrics.org">ofiwg-bounces@lists.openfabrics.org</a> [mailto:<a href="mailto:ofiwg-">ofiwg-</a><br>
> <a href="mailto:bounces@lists.openfabrics.org">bounces@lists.openfabrics.org</a>] On Behalf Of Hefty, Sean<br>
> Sent: Wednesday, October 28, 2015 3:14 PM<br>
> To: Hefty, Sean <<a href="mailto:sean.hefty@intel.com">sean.hefty@intel.com</a>>; Howard Pritchard<br>
> <<a href="mailto:hppritcha@gmail.com">hppritcha@gmail.com</a>><br>
> Cc: <a href="mailto:ofiwg@lists.openfabrics.org">ofiwg@lists.openfabrics.org</a><br>
> Subject: Re: [ofiwg] strided IOVs<br>
><br>
> > I need more context to understand how writing X bytes every N bytes<br>
> > into a one-time use receive buffer is useful.<br>
><br>
> FWIW, someone sent me this link:<br>
><br>
> <a href="http://people.csail.mit.edu/fred/ghost_cell.pdf" target="_blank">http://people.csail.mit.edu/fred/ghost_cell.pdf</a><br>
><br>
> as an example.<br>
> _______________________________________________<br>
> ofiwg mailing list<br>
> <a href="mailto:ofiwg@lists.openfabrics.org">ofiwg@lists.openfabrics.org</a><br>
> <a href="http://lists.openfabrics.org/mailman/listinfo/ofiwg" target="_blank">http://lists.openfabrics.org/mailman/listinfo/ofiwg</a><br>
_______________________________________________<br>
ofiwg mailing list<br>
<a href="mailto:ofiwg@lists.openfabrics.org">ofiwg@lists.openfabrics.org</a><br>
<a href="http://lists.openfabrics.org/mailman/listinfo/ofiwg" target="_blank">http://lists.openfabrics.org/mailman/listinfo/ofiwg</a><o:p></o:p></p>
</div>
</div>
</blockquote>
</div>
<p class="MsoNormal"><br>
<br clear="all">
<o:p></o:p></p>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<p class="MsoNormal">-- <o:p></o:p></p>
<div>
<p class="MsoNormal">Jeff Hammond<br>
<a href="mailto:jeff.science@gmail.com" target="_blank">jeff.science@gmail.com</a><br>
<a href="http://jeffhammond.github.io/" target="_blank">http://jeffhammond.github.io/</a><o:p></o:p></p>
</div>
</div>
</div>
</div>
</body>
</html>