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Try faster double-to-string algo; not good enuf
grisu.net is the best third-party alternative I found for converting doubles to strings, but as "most recent errors.txt" shows, there are some numbers that do not round-trip to the same value, like how 7.2600388277351625E-72 is dumped as 7.260038827735163e-72, which is not quite the same. Interestingly, Python says they're the same, but C# disagrees, and that's disqualifying enough for me. I will create this branch to reflect my current best effort to improve double-to-string performance, but I will not be incorporating this into my main branch.
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| // Copyright 2010 the V8 project authors. All rights reserved. | ||
| // Copyright 2011-2012, Kevin Ring. All rights reserved. | ||
| // Redistribution and use in source and binary forms, with or without | ||
| // modification, are permitted provided that the following conditions are | ||
| // met: | ||
| // | ||
| // * Redistributions of source code must retain the above copyright | ||
| // notice, this list of conditions and the following disclaimer. | ||
| // * Redistributions in binary form must reproduce the above | ||
| // copyright notice, this list of conditions and the following | ||
| // disclaimer in the documentation and/or other materials provided | ||
| // with the distribution. | ||
| // * Neither the name of Google Inc. nor the names of its | ||
| // contributors may be used to endorse or promote products derived | ||
| // from this software without specific prior written permission. | ||
| // | ||
| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | ||
| // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | ||
| // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | ||
| // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | ||
| // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | ||
| // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT | ||
| // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | ||
| // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | ||
| // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | ||
| // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | ||
| // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | ||
|
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| using System.Diagnostics; | ||
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| namespace GrisuDotNet | ||
| { | ||
| // This "Do It Yourself Floating Point" class implements a floating-point number | ||
| // with a uint64 significand and an int exponent. Normalized DiyFp numbers will | ||
| // have the most significant bit of the significand set. | ||
| // Multiplication and Subtraction do not normalize their results. | ||
| // DiyFp are not designed to contain special doubles (NaN and Infinity). | ||
| internal struct DiyFp | ||
| { | ||
| public const int kSignificandSize = 64; | ||
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| public DiyFp(ulong f, int e) | ||
| { | ||
| f_ = f; | ||
| e_ = e; | ||
| } | ||
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| // this = this - other. | ||
| // The exponents of both numbers must be the same and the significand of this | ||
| // must be bigger than the significand of other. | ||
| // The result will not be normalized. | ||
| public void Subtract(ref DiyFp other) | ||
| { | ||
| Debug.Assert(e_ == other.e_); | ||
| Debug.Assert(f_ >= other.f_); | ||
| f_ -= other.f_; | ||
| } | ||
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| // Returns a - b. | ||
| // The exponents of both numbers must be the same and this must be bigger | ||
| // than other. The result will not be normalized. | ||
| public static DiyFp Minus(ref DiyFp a, ref DiyFp b) | ||
| { | ||
| DiyFp result = a; | ||
| result.Subtract(ref b); | ||
| return result; | ||
| } | ||
|
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|
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| // this = this * other. | ||
| public void Multiply(ref DiyFp other) | ||
| { | ||
| // Simply "emulates" a 128 bit multiplication. | ||
| // However: the resulting number only contains 64 bits. The least | ||
| // significant 64 bits are only used for rounding the most significant 64 | ||
| // bits. | ||
| const ulong kM32 = 0xFFFFFFFFU; | ||
| ulong a = f_ >> 32; | ||
| ulong b = f_ & kM32; | ||
| ulong c = other.f_ >> 32; | ||
| ulong d = other.f_ & kM32; | ||
| ulong ac = a * c; | ||
| ulong bc = b * c; | ||
| ulong ad = a * d; | ||
| ulong bd = b * d; | ||
| ulong tmp = (bd >> 32) + (ad & kM32) + (bc & kM32); | ||
| // By adding 1U << 31 to tmp we round the final result. | ||
| // Halfway cases will be round up. | ||
| tmp += 1U << 31; | ||
| ulong result_f = ac + (ad >> 32) + (bc >> 32) + (tmp >> 32); | ||
| e_ += other.e_ + 64; | ||
| f_ = result_f; | ||
| } | ||
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| // returns a * b; | ||
| public static DiyFp Times(ref DiyFp a, ref DiyFp b) | ||
| { | ||
| DiyFp result = a; | ||
| result.Multiply(ref b); | ||
| return result; | ||
| } | ||
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| public void Normalize() | ||
| { | ||
| Debug.Assert(f_ != 0); | ||
| ulong f = f_; | ||
| int e = e_; | ||
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| // This method is mainly called for normalizing boundaries. In general | ||
| // boundaries need to be shifted by 10 bits. We thus optimize for this case. | ||
| const ulong k10MSBits = 0xFFC0000000000000; | ||
| while ((f & k10MSBits) == 0) | ||
| { | ||
| f <<= 10; | ||
| e -= 10; | ||
| } | ||
| while ((f & kUint64MSB) == 0) | ||
| { | ||
| f <<= 1; | ||
| e--; | ||
| } | ||
| f_ = f; | ||
| e_ = e; | ||
| } | ||
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| public static DiyFp Normalize(ref DiyFp a) | ||
| { | ||
| DiyFp result = a; | ||
| result.Normalize(); | ||
| return result; | ||
| } | ||
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| public ulong F | ||
| { | ||
| get { return f_; } | ||
| set { f_ = value; } | ||
| } | ||
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| public int E | ||
| { | ||
| get { return e_; } | ||
| set { e_ = value; } | ||
| } | ||
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| private const ulong kUint64MSB = 0x8000000000000000; | ||
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| private ulong f_; | ||
| private int e_; | ||
| } | ||
| } |
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