Fwd: [squeak-dev] The Trunk: Kernel-nice.272.mcz

> From: Nicolas Cellier <[hidden email]>
> Date: October 19, 2009 2:58:30 PM GMT+02:00
> To: Stéphane Ducasse <[hidden email]>, stephane ducasse <[hidden email]
> >
> Subject: Fwd: [squeak-dev] The Trunk: Kernel-nice.272.mcz
>
> Salut,
>
> Minor change to be integrated in pharo...
>
> J'ai une insulte de mail delivery quand j'essaie de transférer à
> [hidden email] ...
>
> Nicolas
>
>
> ---------- Forwarded message ----------
> From:  <[hidden email]>
> Date: 2009/10/19
> Subject: [squeak-dev] The Trunk: Kernel-nice.272.mcz
> To: [hidden email]
>
>
> Nicolas Cellier uploaded a new version of Kernel to project The Trunk:
> http://source.squeak.org/trunk/Kernel-nice.272.mcz
>
> ==================== Summary ====================
>
> Name: Kernel-nice.272
> Author: nice
> Time: 19 October 2009, 2:39:18 am
> UUID: 6ad59bb1-c97b-ad4f-aa05-ae19f0921ca5
> Ancestors: Kernel-ar.271
>
> How to gain a factor x2 on speed of
> String streamContents: [:strm | Float pi absPrintExactlyOn: strm  
> base: 10]
>
> 1) do not use d := r // s.  r := r \\ s. This will evaluate the  
> quotient twice.
> 2) s generally has a lot of trailing bits = 0, so it is faster to  
> evaluate:
> d := (r >> (s lowBit - 1)) // (s >> (s lowBit - 1)).
> especially s lowBit - 1 and (s >> (s lowBit - 1)) can go outside the  
> while loop
> 3) revert the tests in tc1 and tc2: these tests are false but for the
> last digit.
> Since Float usually have more than 2 digits, it is statistically
> faster to test for the false condition first.
> 4) use and: or: when due instead of & |
>
>
> =============== Diff against Kernel-ar.271 ===============
>
> Item was changed:
>  ----- Method: Float>>absPrintExactlyOn:base: (in category  
> 'printing') -----
>  absPrintExactlyOn: aStream base: base
>        "Print my value on a stream in the given base.  Assumes that my
> value is strictly
>        positive; negative numbers, zero, and NaNs have already been
> handled elsewhere.
>        Based upon the algorithm outlined in:
>        Robert G. Burger and R. Kent Dybvig
>        Printing Floating Point Numbers Quickly and Accurately
>        ACM SIGPLAN 1996 Conference on Programming Language Design and
> Implementation
>        June 1996.
>        This version guarantees that the printed representation exactly
> represents my value
>        by using exact integer arithmetic."
>
> +       | fBase significand exp baseExpEstimate be be1 r s mPlus
> mMinus scale roundingIncludesLimits d tc1 tc2 fixedFormat
> decPointCount slowbit shead |
> -       | fBase significand exp baseExpEstimate be be1 r s mPlus
> mMinus scale roundingIncludesLimits d tc1 tc2 fixedFormat
> decPointCount |
>        self isInfinite ifTrue: [aStream nextPutAll: 'Infinity'. ^  
> self].
>        fBase := base asFloat.
>        significand := self significandAsInteger.
>        roundingIncludesLimits := significand even.
>        exp := (self exponent - 52) max: MinValLogBase2.
>        baseExpEstimate := (self exponent * fBase reciprocalLogBase2 -
> 1.0e-10) ceiling.
>        exp >= 0
>                ifTrue:
>                        [be := 1 << exp.
>                        significand ~= 16r10000000000000
>                                ifTrue:
>                                        [r := significand * be * 2.
>                                        s := 2.
>                                        mPlus := be.
>                                        mMinus := be]
>                                ifFalse:
>                                        [be1 := be * 2.
>                                        r := significand * be1 * 2.
>                                        s := 4.
>                                        mPlus := be1.
>                                        mMinus := be]]
>                ifFalse:
> +                       [(exp = MinValLogBase2 or: [significand ~=
> 16r10000000000000])
> -                       [(exp = MinValLogBase2) | (significand ~=
> 16r10000000000000)
>                                ifTrue:
>                                        [r := significand * 2.
>                                        s := (1 << (exp negated)) * 2.
>                                        mPlus := 1.
>                                        mMinus := 1]
>                                ifFalse:
>                                        [r := significand * 4.
>                                        s := (1 << (exp negated + 1))  
> * 2.
>                                        mPlus := 2.
>                                        mMinus := 1]].
>        baseExpEstimate >= 0
>                ifTrue: [s := s * (base raisedToInteger:  
> baseExpEstimate)]
>                ifFalse:
>                        [scale := base raisedToInteger:  
> baseExpEstimate negated.
>                        r := r * scale.
>                        mPlus := mPlus * scale.
>                        mMinus := mMinus * scale].
> +       ((r + mPlus < s) not and: [roundingIncludesLimits or: [r +  
> mPlus > s]])
> -       (r + mPlus > s) | (roundingIncludesLimits & (r + mPlus = s))
>                ifTrue: [baseExpEstimate := baseExpEstimate + 1]
>                ifFalse:
>                        [r := r * base.
>                        mPlus := mPlus * base.
>                        mMinus := mMinus * base].
>        (fixedFormat := baseExpEstimate between: -3 and: 6)
>                ifTrue:
>                        [decPointCount := baseExpEstimate.
>                        baseExpEstimate <= 0
>                                ifTrue: [aStream nextPutAll:
> ('0.000000' truncateTo: 2 - baseExpEstimate)]]
>                ifFalse:
> +                       [decPointCount := 1].
> +       slowbit := s lowBit - 1.
> +       shead := s >> slowbit.
> +       [d := (r >> slowbit) // shead.
> +       r := r - (d*s).
> +       (tc1 := (r > mMinus) not and: [roundingIncludesLimits or: [r <
> mMinus]]) |
> +       (tc2 := (r + mPlus < s) not and: [roundingIncludesLimits or:
> [r + mPlus > s]])] whileFalse:
> -                       [decPointCount := 1].
> -       [d := r // s.
> -       r := r \\ s.
> -       (tc1 := (r < mMinus) | (roundingIncludesLimits & (r =  
> mMinus))) |
> -       (tc2 := (r + mPlus > s) | (roundingIncludesLimits & (r + mPlus
> = s)))] whileFalse:
>                [aStream nextPut: (Character digitValue: d).
>                r := r * base.
>                mPlus := mPlus * base.
>                mMinus := mMinus * base.
>                decPointCount := decPointCount - 1.
>                decPointCount = 0 ifTrue: [aStream nextPut: $.]].
>        tc2 ifTrue:
> +               [(tc1 not or: [r*2 >= s]) ifTrue: [d := d + 1]].
> -               [tc1 not | (tc1 & (r*2 >= s)) ifTrue: [d := d + 1]].
>        aStream nextPut: (Character digitValue: d).
>        decPointCount > 0
>                ifTrue:
>                [decPointCount - 1 to: 1 by: -1 do: [:i | aStream  
> nextPut: $0].
>                aStream nextPutAll: '.0'].
>        fixedFormat ifFalse:
>                [aStream nextPut: $e.
>                aStream nextPutAll: (baseExpEstimate - 1) printString]!