Instead of computing the final adjustment factor as a power of 10,
it's more efficient to split 10**e into 2**e * 5**e . Powers of 2
are trivially added to the Float exponent, and powers of 5 are
smaller and thus faster to compute.
Also, use a table of uint64 values rather than float64 values for
initial power value. uint64 values appear to be faster to convert
to Floats (useful for small exponents).
Added two small benchmarks to confirm that there's no regresssion.
benchmark old ns/op new ns/op delta
BenchmarkParseFloatSmallExp-8 17543 16220 -7.54%
BenchmarkParseFloatLargeExp-8 60865 59996 -1.43%
Change-Id: I3efd7556b023316f86f334137a67fe0c6d52f8ef
Reviewed-on: https://go-review.googlesource.com/14782
Reviewed-by: Alan Donovan <adonovan@google.com>
Even though the umul/uquo functions expect two valid, finite big.Floats
arguments, SetString was calling them with possibly Inf values, which
resulted in bogus return values.
Replace umul and udiv calls with Mul and Quo calls to fix this. Also,
fix two wrong tests.
See relevant issue on issue tracker for a detailed explanation.
Fixes#11341
Change-Id: Ie35222763a57a2d712a5f5f7baec75cab8189a53
Reviewed-on: https://go-review.googlesource.com/13778
Reviewed-by: Robert Griesemer <gri@golang.org>
- (*Float).Scan conflicted with fmt.Scanner.Scan; it was also only used
internally. Removed it, as well as the companion ScanFloat function.
- (*Float).Parse (and thus ParseFloat) can now also parse infinities.
As a result, more code could be simplified.
- Fixed a bug in rounding (round may implicitly be called for infinite
values). Found via existing test cases, after simplifying some code.
- Added more test cases.
Fixes issue #10938.
Change-Id: I1df97821654f034965ba8b82b272e52e6dc427f1
Reviewed-on: https://go-review.googlesource.com/10498
Reviewed-by: Alan Donovan <adonovan@google.com>
- factor out handling of sign
- rename bstring, pstring to fmtB, fmtP consistent with fmtE, fmtF
- move all float-to-string conversion functions into ftoa.go
- no functional changes
Change-Id: I5970ecb874dc9c387630b59147d90bda16a5d8e6
Reviewed-on: https://go-review.googlesource.com/10387
Reviewed-by: Alan Donovan <adonovan@google.com>
Float.Format supports the 'b' and 'p' format, both of which print
a binary ('p') exponent. The 'b' format always printed a sign ('+'
or '-') for the exponent; the 'p' format only printed a negative
sign for the exponent. This change makes the two consistent. It
also makes the 'p' format easier to read if the exponent is >= 0.
Also:
- Comments added elsewhere.
Change-Id: Ifd2e01bdafb3043345972ca22a90248d055bd29b
Reviewed-on: https://go-review.googlesource.com/10359
Reviewed-by: Alan Donovan <adonovan@google.com>
NaNs make the API more complicated for no real good reasons.
There are few operations that produce NaNs with IEEE arithmetic,
there's no need to copy the behavior. It's easy to test for these
scenarios and avoid them (on the other hand, it's not easy to test
for overflow or underflow, so we want to keep +/-Inf).
Also:
- renamed IsNeg -> Signbit (clearer, especially for x == -0)
- removed IsZero (Sign() == 0 is sufficient and efficient)
- removed IsFinite (now same as !IsInf)
Change-Id: I3f3b4445c325d9bbb1bf46ce2e298a6aeb498e07
Reviewed-on: https://go-review.googlesource.com/8280
Reviewed-by: Alan Donovan <adonovan@google.com>
This is a fairly significant _internal_ representation change. Instead
of encoding 0, finite, infinite, and NaN values with special mantissa
and exponent values, a new (1 byte) 'form' field is used (without making
the Float struct bigger). The form field permits simpler and faster
case distinctions. As a side benefit, for zero and non-finite floats,
fewer fields need to be set. Also, the exponent range is not the full
int32 range (in the old format, infExp and nanExp were used to represent
Inf and NaN values and tests for those values sometimes didn't test
for the empty mantissa, so the range was reduced by 2 values).
The correspondence between the old and new fields is as follows.
Old representation:
x neg mant exp
---------------------------------------------------------------
+/-0 sign empty 0
0 < |x| < +Inf sign mantissa exponent
+/-Inf sign empty infExp
NaN false empty nanExp
New representation (- stands for ignored fields):
x neg mant exp form
---------------------------------------------------------------
+/-0 sign - - zero
0 < |x| < +Inf sign mantissa exponent finite
+/-Inf sign - - inf
NaN - - - nan
Client should not be affected by this change.
Change-Id: I7e355894d602ceb23f9ec01da755fe6e0386b101
Reviewed-on: https://go-review.googlesource.com/6870
Reviewed-by: Alan Donovan <adonovan@google.com>
This change introduces NaNs (for situations like Inf-Inf, etc.).
The implementation is incomplete (the four basic operations produce
a NaN if any of the operands is an Inf or a NaN); and some operations
produce incorrect accuracy for NaN arguments. These are known bugs
which are documented.
Change-Id: Ia88841209e47930681cef19f113e178f92ceeb33
Reviewed-on: https://go-review.googlesource.com/6540
Reviewed-by: Alan Donovan <adonovan@google.com>
Also: remove NewFloat - not needed anymore. Work-around for places
where has been used so far:
NewFloat(x, prec, mode) === new(Float).SetMode(mode).SetPrec(prec).SetFloat64(x)
However, if mode == ToNearestEven, SetMode is not needed. SetPrec
is needed if the default precision (53 after SetFloat64) is not
adequate.
TBR adonovan
Change-Id: Ifda12c479ba157f2dea306c32b47c7afbf31e759
Reviewed-on: https://go-review.googlesource.com/4842
Reviewed-by: Robert Griesemer <gri@golang.org>
Also:
- make representation more flexible (no need to store trailing 0 digits to match precision)
- simplify rounding as a consequence
- minor related fixes
TBR adonovan
Change-Id: Ie91075990688b506d28371ec3b633b8267397ebb
Reviewed-on: https://go-review.googlesource.com/4841
Reviewed-by: Rob Pike <r@golang.org>
- Frexp, Ldexp are equivalents to the corresponding math functions.
- Set now has the same prec behavior as the other functions
- Copy is a true assignment (replaces old version of Set)
- Cmp now handles infinities
- more tests
Change-Id: I0d33980c08be3095b25d7b3d16bcad1aa7abbd0f
Reviewed-on: https://go-review.googlesource.com/4292
Reviewed-by: Alan Donovan <adonovan@google.com>
- clarified representation of +/-Inf
- only 0 and Inf values can have 0 precision
- a zero precision value used as result value takes the max precision
of the arguments (to be fine-tuned for setters)
- the zero precision approach makes Float zero values possible
(they represent +0)
- more tests
Missing: Filling in the blanks. More tests.
Change-Id: Ibb4f97e12e1f356c3085ce80f3464e97b82ac130
Reviewed-on: https://go-review.googlesource.com/4000
Reviewed-by: Alan Donovan <adonovan@google.com>
(For zero values the strconv %b format prints the bias-adjusted exponent;
there's no bias in Float.)
Change-Id: I6f4dda9c3a50d02eac375cfe2c927c1540aae865
Reviewed-on: https://go-review.googlesource.com/3841
Reviewed-by: Alan Donovan <adonovan@google.com>
No other functional changes.
Change-Id: I7e0bb7452c6a265535297ec7ce6a629f1aff695c
Reviewed-on: https://go-review.googlesource.com/3674
Reviewed-by: Alan Donovan <adonovan@google.com>
Martin Möhrmann
Robert Griesemer
Alberto Donizetti