<html><body><p><font size="2">Mike,</font><br><br><font size="2">I don't remember defining the sameQuantum operation. </font><br><font size="2">I think it was to compare exponents or as a compare units instruction </font><br><font size="2">and used it to determine whether the result had the expected quantum. </font><br><font size="2">This was before IBM architecture came up with a flag for quantum exceptions and</font><br><font size="2">before we figured out we could test the most significant digit for non-zero.</font><br><font size="2">So if we are just testing a result for correct units, we don't want to trigger exceptions,</font><br><font size="2">though we may want to force it into the correct units.</font><br><font size="2">An example is we have a table of data to output that should have the units of 10^-2, we</font><br><font size="2">test each data item before converting the significand to BCD and outputting the</font><br><font size="2">data. Probably figured SNaNs would have already been seen by this point and</font><br><font size="2">not a point in the program where we want to take any exceptions.</font><br><font size="2"><br>Regards,<br>Eric<br><br><br>eschwarz@us.ibm.com</font><br><br><tt><font size="2">"Mike Cowlishaw" <mfc@speleotrove.com> wrote on 09/17/2018 06:47:19 AM:<br><br>> From: "Mike Cowlishaw" <mfc@speleotrove.com></font></tt><br><tt><font size="2">> To: "'Jim Thomas'" <jaswthomas@sbcglobal.net></font></tt><br><tt><font size="2">> Cc: <cfp-interest@oakapple.net>, "'Eric Schwarz'" <eschwarz@us.ibm.com></font></tt><br><tt><font size="2">> Date: 09/17/2018 06:47 AM</font></tt><br><tt><font size="2">> Subject: RE: [Cfp-interest] Not trigger sNaN</font></tt><br><tt><font size="2">> <br>> I believe it was, but I do not recall the reasoning. Eric Schwartz might<br>> remember; cc:ing him ...<br>> <br>> Mike <br>> <br>> > -----Original Message-----<br>> > From: Jim Thomas [<a href="mailto:jaswthomas@sbcglobal.net">mailto:jaswthomas@sbcglobal.net</a>] <br>> > Sent: 16 September 2018 16:40<br>> > To: Mike Cowlishaw<br>> > Cc: cfp-interest@oakapple.net<br>> > Subject: Re: [Cfp-interest] Not trigger sNaN<br>> > <br>> > Mike,<br>> > <br>> > 754 seems to say sameQuantum(sNaN, qNaN) is true with no <br>> > exception. Just double checking that it is as intended.<br>> > <br>> > Jim<br>> > <br>> > > On Aug 28, 2018, at 7:16 PM, Fred J. Tydeman <br>> > <tydeman@tybor.com> wrote:<br>> > > <br>> > > On Tue, 28 Aug 2018 13:13:45 -0500 Rajan Bhakta wrote:<br>> > >> <br>> > >> *AI*: Fred: See which other functions have the need to not <br>> > >> trigger signaling nans but are functions (need to be macros).<br>> > > <br>> > > 754 Operations that shall not trigger an sNaN (signal invalid):<br>> > > <br>> > > "*" are functions in C<br>> > > <br>> > > <br>> > ...<br>> > > sameQuantum() = samequantum()*<br>> > > <br>> > <br>> <br></font></tt><BR>
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