<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">The following is from a side-discussion about Pavel Morozkin’s suggestion to change the titles of 7.12.13 and F.10.10 from “Floating multiply-add” to “Fused multiply-add”, which will be on the CFP agenda for March.<div class=""><br class=""></div><div class="">- Jim Thomas<br class=""><div><br class=""><blockquote type="cite" class=""><div class="">Begin forwarded message:</div><br class="Apple-interchange-newline"><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px;" class=""><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif; color:rgba(0, 0, 0, 1.0);" class=""><b class="">From: </b></span><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif;" class="">Pavel M <<a href="mailto:pavel.morozkin@gmail.com" class="">pavel.morozkin@gmail.com</a>><br class=""></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px;" class=""><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif; color:rgba(0, 0, 0, 1.0);" class=""><b class="">Subject: </b></span><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif;" class=""><b class="">Re: Terminology: why "floating multiply-add" instead of "fused multiply-add"?</b><br class=""></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px;" class=""><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif; color:rgba(0, 0, 0, 1.0);" class=""><b class="">Date: </b></span><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif;" class="">March 2, 2022 at 4:19:51 PM PST<br class=""></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px;" class=""><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif; color:rgba(0, 0, 0, 1.0);" class=""><b class="">To: </b></span><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif;" class="">Jim Thomas <<a href="mailto:jaswthomas@sbcglobal.net" class="">jaswthomas@sbcglobal.net</a>><br class=""></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px;" class=""><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif; color:rgba(0, 0, 0, 1.0);" class=""><b class="">Cc: </b></span><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif;" class="">"Fred J. Tydeman" <<a href="mailto:tydeman@tybor.com" class="">tydeman@tybor.com</a>>, Rajan Bhakta <<a href="mailto:rbhakta@us.ibm.com" class="">rbhakta@us.ibm.com</a>>, Jens Gustedt <<a href="mailto:jens.gustedt@inria.fr" class="">jens.gustedt@inria.fr</a>><br class=""></span></div><br class=""><div class=""><div dir="ltr" class=""><div dir="ltr" class="">Jim,<br class=""></div><br class=""><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, 1 Mar 2022 at 19:50, Jim Thomas <<a href="mailto:jaswthomas@sbcglobal.net" class="">jaswthomas@sbcglobal.net</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="overflow-wrap: break-word;" class=""><div class=""><div class=""><blockquote type="cite" class=""><div class="">On Feb 28, 2022, at 10:27 AM, Pavel M <<a href="mailto:pavel.morozkin@gmail.com" target="_blank" class="">pavel.morozkin@gmail.com</a>> wrote:</div><br class=""><div class=""><div dir="ltr" class="">Jim,<br class=""><br class="">In FMAD the F stands for "fused". However, we see that fmadXX are in section "Floating multiply-add":<br class=""><span id="gmail-m_3038084323866342742cid:ii_l0716oel0" class=""><image.png></span><br class="">Here the "f" could easily be misinterpreted as "floating" as opposed to its actual meaning "fused".<br class=""><div class="">In my view the section needs to be named "Fused multiply-add".<br class=""></div></div></div></blockquote><div class=""><br class=""></div>I believe we basically agree. I’d say that given the subclause title "Floating multiply-add” the “f” would naturally be read as “floating”. However, the description of the function clearly states that the mathematical result of the multiply-add is rounded just once, i.e. the C floating multiply-add is a fused operation. “Fused multiply-add” would be a more specific title for the subclause, would reflect industry terminology, and might reduce mental dissonance.<br class=""></div></div></div></blockquote><div class="">Well said. Seems nothing to change / add.</div><div class=""><br class=""></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="overflow-wrap: break-word;" class=""><div class=""><div class=""></div><div class=""><br class=""></div><div class="">CFP will discuss it and decide whether to submit a late proposal for the change.</div></div></div></blockquote><div class="">OK.<br class=""></div><div class=""> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="overflow-wrap: break-word;" class=""><div class=""><div class="">Would you have any objection to my forwarding this thread to CFP as background of the discussion?</div></div></div></blockquote><div class="">No
objection.</div><div class=""><br class=""></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="overflow-wrap: break-word;" class=""><div class=""><div class=""><br class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class=""><br class=""></div><div class="">Or maybe it is me who is missing a point: after the C standard will be fixed (Floating => Fused), the "extension documents" will be fixed as well.</div><div class="">Is that correct?<br class=""></div></div></div></blockquote><div class=""><br class=""></div><div class="">The relevant extension documents are being incorporated into (and superseded by) C23, so I wouln’t expect them to be revised.</div></div></div></div></blockquote><div class="">And what about <b class="">the next revisions</b> of the
relevant extension documents? I think that the
extension documents need to be (eventually) fixed too. This is to maintain consistency in terminology.<br class=""><br class="">--<br class=""></div><div class="">Pavel<br class=""></div><div class=""> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="overflow-wrap: break-word;" class=""><div class=""><div class=""><div class=""><br class=""></div><div class="">- Jim</div><div class=""><br class=""></div><blockquote type="cite" class=""><div class=""><br class=""><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, 25 Feb 2022 at 08:48, Jim Thomas <<a href="mailto:jaswthomas@sbcglobal.net" target="_blank" class="">jaswthomas@sbcglobal.net</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="">Pavel,<div class=""><br class=""></div><div class="">I might be missing a point here. The document you mention uses “fused” referring to the fused multiply-add operation in IEEE 754. C uses floating multiply-add to refer to the C function that corresponds to this IEEE 754 fused multiply-add operation. One of the historical C naming styles is prefixing a function name with f to indicate floating. The fabs, fmod, and fmax functions are examples. The fma function seen in the same way is naturally called floating multiply-add. One might argue that calling it fused multiple-add would better suggest the important “fused” behavior of the function. I understand this point. Is there another one?</div><div class=""><br class=""></div><div class="">- Jim Thomas</div><div class=""><br class=""><blockquote type="cite" class=""><div class="">On Feb 24, 2022, at 5:17 AM, Pavel M <<a href="mailto:pavel.morozkin@gmail.com" target="_blank" class="">pavel.morozkin@gmail.com</a>> wrote:</div><br class=""><div class=""><div dir="ltr" class="">Jim,<div class=""><br class="">Thanks.<br class=""><br class="">Also: Document "Extension for the programming language C to support decimal floating-point arithmetic" [1] uses FMAD / fmad, and F / f has meaning "fused" (emphasis added):<br class="">[7] The macro</div><div class="">FP_FAST_<b class="">FMAD</b>32</div><div class="">FP_FAST_<b class="">FMAD</b>64</div><div class="">FP_FAST_<b class="">FMAD</b>128<br class="">are, respectively, _Decimal32, _Decimal64 and _Decimal128 analogs of FP_FAST_<b class="">FMA</b>. <br class=""><br class="">However, later in the document there is (emphasis added):</div><div class=""> 7.12.13 <b class="">Floating </b>multiply-add</div><div class="">_Decimal64 <b class="">fmad</b>64(_Decimal64 x, _Decimal64 y, _Decimal64 z);</div><div class="">_Decimal32 <b class="">fmad</b>32(_Decimal32 x, _Decimal32 y, _Decimal32 z);</div><div class="">_Decimal128 <b class="">fmad</b>128(_Decimal128 x, _Decimal128 y, _Decimal128 z);<br class=""><br class="">Here the "f" could easily be misinterpreted as "floating" as opposed to its actual meaning "fused".<br class=""></div><div class=""><br class="">Please fix it.<br class=""><br class="">[1] <a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1154.pdf" target="_blank" class="">http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1154.pdf</a></div></div><br class=""><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, 24 Feb 2022 at 05:02, Jim Thomas <<a href="mailto:jaswthomas@sbcglobal.net" target="_blank" class="">jaswthomas@sbcglobal.net</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="">Hi Pavel,<div class=""><br class=""></div><div class="">I’ll put this on the agenda for the March CFP meeting.</div><div class=""><br class=""></div><div class="">I believe the reason for using “floating multiply-add” was to distinguish it from an integer multiply-add. Using “fused multiply-add” might be more suggestive of its single rounding.</div><div class=""><br class=""></div><div class="">- Jim Thomas<br class=""><div class=""><br class=""><blockquote type="cite" class=""><div class="">On Feb 23, 2022, at 3:49 AM, Pavel M <<a href="mailto:pavel.morozkin@gmail.com" target="_blank" class="">pavel.morozkin@gmail.com</a>> wrote:</div><br class=""><div class=""><div dir="ltr" class="">Any <span class="">updates</span>?<br class=""></div><br class=""><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, 2 Feb 2022 at 16:21, Pavel M <<a href="mailto:pavel.morozkin@gmail.com" target="_blank" class="">pavel.morozkin@gmail.com</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr" class="">Hello Fred,<br class=""><br class="">C11 (and newer):<br class="">> 7.12.13 Floating multiply-add<br class=""><br class="">IEEE 754-2008:<br class="">> fused multiply add, fusedMultiplyAdd<br class=""><br class="">Wikipedia:<br class="">> fused multiply-add<br class=""><br class="">Why C11 (and newer) uses "floating multiply-add" instead of "fused multiply-add"?<div class="">Does it need to be changed?</div><div class="">Is it better to change?<br class=""><div class=""><br class=""></div><div class="">--</div><div class="">Pavel</div></div></div>
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