<div dir="ltr">Hi Nicolas,<br><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Mar 6, 2015 at 10:35 AM, Nicolas Cellier <span dir="ltr"><<a href="mailto:ncellier@ifrance.com" target="_blank">ncellier@ifrance.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"> <br><div dir="ltr"><div><div><div><div><div><div><div><div><div><div><div><div>I'm trying to understand the negative case...<br><br></div>We have the magnitude on one side xMag<br></div>We minSmallInteger in two complement on the other side yTC<br></div>We know that the magnitude of minSmallInteger is yMag=bitInvert(yTC)+1<br></div>We know that all bytes of yTC are 0 but the MSB<br></div>Thus all bytes of bitInvert(yTC) are 16rFF<br></div>Thus all bytes of yMag are 0, but the highest which is (MSB(yTC) xOr: 256) + 1.<br><br></div>Thus, assuming same byte length:<br>MSB(xMag) < MSB(yMag) => x is a CSI<br>MSB(xMag) > MSB(yMag) => x is large<br>MSB(xMag) = MSB(yMag) => we must inquire the LSBs of xMag..<br></div>(1 to: len-1) anySatisfy: [:i | (xMag digitAt: i) ~= 0] => x isLarge<br></div>otherwise, x is minSmallInteger<br><br></div>Eliot, I fail to see the bitInvert(MSB(minSmallInteger))+1 in your code...<br></div>Did I miss something?<br></div></div></blockquote><div><br></div><div>You're talking about normalizeNegative: right? I haven't changed anything fundamental here. The check is in</div><div><br></div><div><div><span class="" style="white-space:pre"> </span>len <= sLen ifTrue: </div><div><span class="" style="white-space:pre"> </span>[(len < sLen</div><div><span class="" style="white-space:pre"> </span> or: [(pointer at: sLen - 1)</div><div><span class="" style="white-space:pre"> </span>< (self cDigitOfCSI: interpreterProxy minSmallInteger at: sLen)]) ifTrue: "interpreterProxy minSmallInteger lastDigit"</div><div><span class="" style="white-space:pre"> </span>["If high digit less, then can be small"</div><div><span class="" style="white-space:pre"> </span>val := 0 - (pointer at: (len := len - 1)).</div><div><span class="" style="white-space:pre"> </span>len - 1 to: 0 by: -1 do:</div><div><span class="" style="white-space:pre"> </span>[:i | val := val * 256 - (pointer at: i)].</div><div><span class="" style="white-space:pre"> </span>^val asOop: SmallInteger].</div><div><span class="" style="white-space:pre"> </span> 1 to: sLen do:</div><div><span class="" style="white-space:pre"> </span>[:i | | byte | "If all digits same, then = minSmallInteger (sr: minSmallInteger digits 1 to sLen - 1 are 0)"</div><div><span class="" style="white-space:pre"> </span>byte := i > len ifTrue: [0] ifFalse: [pointer at: i - 1].</div><div><span class="" style="white-space:pre"> </span>byte ~= (self cDigitOfCSI: interpreterProxy minSmallInteger at: i) ifTrue: "Not so; return self shortened"</div><div><span class="" style="white-space:pre"> </span>[len < oldLen ifTrue: "^ self growto: len"</div><div><span class="" style="white-space:pre"> </span>[^self bytes: aLargeNegativeInteger growTo: len].</div><div><span class="" style="white-space:pre"> </span> ^aLargeNegativeInteger]].</div><div><span class="" style="white-space:pre"> </span> ^interpreterProxy minSmallInteger asOop: SmallInteger].</div></div><div><br></div><div>The first part deals with the simple case of something shorter than SmallInteger minVal, or the same length whose top byte is less:</div><div><br></div><div><div><span class="" style="white-space:pre"> </span>(len < sLen</div><div><span class="" style="white-space:pre"> </span> or: [(pointer at: sLen - 1)</div><div><span class="" style="white-space:pre"> </span>< (self cDigitOfCSI: interpreterProxy minSmallInteger at: sLen)]) ifTrue: "interpreterProxy minSmallInteger lastDigit"</div><div><span class="" style="white-space:pre"> </span>["If high digit less, then can be small"</div><div><span class="" style="white-space:pre"> </span>val := 0 - (pointer at: (len := len - 1)).</div><div><span class="" style="white-space:pre"> </span>len - 1 to: 0 by: -1 do:</div><div><span class="" style="white-space:pre"> </span>[:i | val := val * 256 - (pointer at: i)].</div><div><span class="" style="white-space:pre"> </span>^val asOop: SmallInteger].</div></div><div><br></div><div> The second part deals with the possibility of SmallInteger minVal:</div><div><br></div><div><div><div><span class="" style="white-space:pre"> </span> 1 to: sLen do:</div><div><span class="" style="white-space:pre"> </span>[:i | | byte | "If all digits same, then = minSmallInteger (sr: minSmallInteger digits 1 to sLen - 1 are 0)"</div><div><span class="" style="white-space:pre"> </span>byte := i > len ifTrue: [0] ifFalse: [pointer at: i - 1].</div><div><span class="" style="white-space:pre"> </span>byte ~= (self cDigitOfCSI: interpreterProxy minSmallInteger at: i) ifTrue: "Not so; return self shortened"</div><div><span class="" style="white-space:pre"> </span>[len < oldLen ifTrue: "^ self growto: len"</div><div><span class="" style="white-space:pre"> </span>[^self bytes: aLargeNegativeInteger growTo: len].</div><div><span class="" style="white-space:pre"> </span> ^aLargeNegativeInteger]].</div><div><span class="" style="white-space:pre"> </span> ^interpreterProxy minSmallInteger asOop: SmallInteger].</div></div></div><div><br></div><div>The bit invert is in cDigitOfCSI:at: </div><div><span style="white-space:pre"> </span>cDigitOfCSI: csi at: ix <br></div><div><div><span style="white-space:pre"> ^</span>(csi < 0</div><div><span class="" style="white-space:pre"> </span>ifTrue: [0 - csi]</div><div><span class="" style="white-space:pre"> </span>ifFalse: [csi]) >> (ix - 1 * 8) bitAnd: 255</div></div><div><br></div><div>answers 64 for "self cDigitOfCSI: interpreterProxy minSmallInteger at: 4" in 32 bits (16 in 64-bits). So cDigitOfCSI:at: is answering magnitude, not 2's complement bytes.</div><div><br></div><div>Here's the original code before I streamlined it. I don't see a significant difference:</div><div><br></div><div><div><span class="" style="white-space:pre"> </span>len <= sLen</div><div><span class="" style="white-space:pre"> </span>ifTrue: </div><div><span class="" style="white-space:pre"> </span>["SmallInteger minVal"</div><div><span class="" style="white-space:pre"> </span>minVal := interpreterProxy minSmallInteger.</div><div><span class="" style="white-space:pre"> </span>(len < sLen or: [(self digitOfBytes: aLargeNegativeInteger at: sLen)</div><div><span class="" style="white-space:pre"> </span>< (self cDigitOfCSI: minVal at: sLen)</div><div><span class="" style="white-space:pre"> </span>"minVal lastDigit"])</div><div><span class="" style="white-space:pre"> </span>ifTrue: </div><div><span class="" style="white-space:pre"> </span>["If high digit less, then can be small"</div><div><span class="" style="white-space:pre"> </span>val := 0.</div><div><span class="" style="white-space:pre"> </span>len</div><div><span class="" style="white-space:pre"> </span>to: 1</div><div><span class="" style="white-space:pre"> </span>by: -1</div><div><span class="" style="white-space:pre"> </span>do: [:i | val := val * 256 - (self unsafeByteOf: aLargeNegativeInteger at: i)].</div><div><span class="" style="white-space:pre"> </span>^ val asOop: SmallInteger].</div><div><span class="" style="white-space:pre"> </span>1 to: sLen do: [:i | "If all digits same, then = minVal (sr: minVal digits 1 to 3 are 0)"</div><div><span class="" style="white-space:pre"> </span>(self digitOfBytes: aLargeNegativeInteger at: i)</div><div><span class="" style="white-space:pre"> </span>= (self cDigitOfCSI: minVal at: i)</div><div><span class="" style="white-space:pre"> </span>ifFalse: ["Not so; return self shortened"</div><div><span class="" style="white-space:pre"> </span>len < oldLen</div><div><span class="" style="white-space:pre"> </span>ifTrue: ["^ self growto: len"</div><div><span class="" style="white-space:pre"> </span>^ self bytes: aLargeNegativeInteger growTo: len]</div><div><span class="" style="white-space:pre"> </span>ifFalse: [^ aLargeNegativeInteger]]].</div><div><span class="" style="white-space:pre"> </span>^ minVal asOop: SmallInteger].</div></div><div><br></div><div>Or am I misunderstanding?</div><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr"><div><br></div>Nicolas<br></div><div class="gmail_extra"><br><div class="gmail_quote">2015-03-06 0:37 GMT+01:00 Eliot Miranda <span dir="ltr"><<a href="mailto:eliot.miranda@gmail.com" target="_blank">eliot.miranda@gmail.com</a>></span>:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"> <br><div dir="ltr">Hi Nicolas,<div><br></div><div> I found my misunderstanding. Can you review this version instead?</div><div><br></div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Mar 5, 2015 at 11:41 AM, Eliot Miranda <span dir="ltr"><<a href="mailto:eliot.miranda@gmail.com" target="_blank">eliot.miranda@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr">Hi Nicolas,<div><br></div><div> would you mind also reviewing the attached changes? There's a bug in them somewhere, although I think they're close to correct. The ideas here are to</div><div><br></div><div>- avoid calling firstIndexableField: on every call to unsafeByteOf:at: in isNormalized:, normalizePositive: and normalizeNegative:. Do this by cacheing firstIndexableField in a local pointer variable</div><div>- move the bounds check in cDigitOfCSI:at: out to clients that aren't invoking cDigitOfCSI:at: with in-bounds indices</div><div>- avoid the immediate test in digitLengthOf: when it is known that the object is non-immediate. Do so by adding digitLengthOfNonImmediate:.</div><div><br></div><div>Of course this approach can be extended to other LargeIntegers methods, but one step at a time :-/</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Mar 4, 2015 at 2:49 PM, Nicolas Cellier <span dir="ltr"><<a href="mailto:nicolas.cellier.aka.nice@gmail.com" target="_blank">nicolas.cellier.aka.nice@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"> <br><div dir="ltr"><div><div><br>sLen := interpreterProxy minSmallInteger > 16r3FFFFFFF<br><br></div>sounds like a copy/paste error<br></div>I would expect maxSmallInteger here.<br></div>
<br></blockquote></div><span><font color="#888888"><br><br clear="all"><div><br></div>-- <br><div>best,<div>Eliot</div></div>
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</blockquote></div><br><br clear="all"><div><br></div>-- <br><div>best,<div>Eliot</div></div>
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature">best,<div>Eliot</div></div>
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