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faster BigFloat construction for more types #52507

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hycakir
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@hycakir hycakir commented Dec 12, 2023

This pull request addresses #50940 and is a follow-up to #47546.

The changes add Julia construction of BigFloats for some inputs:

  • When the Base.BitInteger64 or Base.IEEEFloat when precision is enough to perfectly represent the input as a BigFloat
  • When the denominator of the Rational is a power of 2.
julia> @btime BigFloat(128)
  14.320 ns (2 allocations: 104 bytes)
128.0

julia> @btime Base.MPFR.BigFloat_mpfr_fallback(128)
  25.518 ns (2 allocations: 104 bytes)
128.0

julia> @btime BigFloat(128.0f0)
  17.952 ns (2 allocations: 104 bytes)
128.0

julia> @btime Base.MPFR.BigFloat_mpfr_fallback(128.0f0)
  35.667 ns (2 allocations: 104 bytes)
128.0

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hycakir commented Jan 11, 2024

@oscardssmith Could you take a look at this?

oscardssmith
oscardssmith reviewed Jan 11, 2024
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nsajko added a commit to nsajko/julia that referenced this pull request Jan 13, 2024
@nsajko
Base: make constructing a float from a rational exact
d2b5d00 
Implementation approach:

1. Convert the (numerator, denominator) pair to a (sign bit, integral
   significand, exponent) triplet using integer arithmetic. The integer
   type in question must be wide enough.

2. Convert the above triplet into an instance of the chosen FP type.
   There is special support for IEEE 754 floating-point and for
   `BigFloat`, otherwise a fallback using `ldexp` is used.

As a bonus, constructing a `BigFloat` from a `Rational` should now be
thread-safe when the rounding mode and precision are provided to the
constructor, because there is no access to the global precision or
rounding mode settings.

Updates JuliaLang#45213

Updates JuliaLang#50940

Updates JuliaLang#52507

Fixes JuliaLang#52394

Closes JuliaLang#52395

Fixes JuliaLang#52859
@nsajko nsajko mentioned this pull request Jan 13, 2024
Open
nsajko added a commit to nsajko/julia that referenced this pull request Jan 14, 2024
@nsajko
Base: make constructing a float from a rational exact
5544f1a 
Implementation approach:

1. Convert the (numerator, denominator) pair to a (sign bit, integral
   significand, exponent) triplet using integer arithmetic. The integer
   type in question must be wide enough.

2. Convert the above triplet into an instance of the chosen FP type.
   There is special support for IEEE 754 floating-point and for
   `BigFloat`, otherwise a fallback using `ldexp` is used.

As a bonus, constructing a `BigFloat` from a `Rational` should now be
thread-safe when the rounding mode and precision are provided to the
constructor, because there is no access to the global precision or
rounding mode settings.

Updates JuliaLang#45213

Updates JuliaLang#50940

Updates JuliaLang#52507

Fixes JuliaLang#52394

Closes JuliaLang#52395

Fixes JuliaLang#52859
nsajko added a commit to nsajko/julia that referenced this pull request Jan 14, 2024
@nsajko
Base: make constructing a float from a rational exact
cc79e0c 
Implementation approach:

1. Convert the (numerator, denominator) pair to a (sign bit, integral
   significand, exponent) triplet using integer arithmetic. The integer
   type in question must be wide enough.

2. Convert the above triplet into an instance of the chosen FP type.
   There is special support for IEEE 754 floating-point and for
   `BigFloat`, otherwise a fallback using `ldexp` is used.

As a bonus, constructing a `BigFloat` from a `Rational` should now be
thread-safe when the rounding mode and precision are provided to the
constructor, because there is no access to the global precision or
rounding mode settings.

Updates JuliaLang#45213

Updates JuliaLang#50940

Updates JuliaLang#52507

Fixes JuliaLang#52394

Closes JuliaLang#52395

Fixes JuliaLang#52859
nsajko added a commit to nsajko/julia that referenced this pull request Jan 14, 2024
@nsajko
Base: make constructing a float from a rational exact
bb7c3ac 
Implementation approach:

1. Convert the (numerator, denominator) pair to a (sign bit, integral
   significand, exponent) triplet using integer arithmetic. The integer
   type in question must be wide enough.

2. Convert the above triplet into an instance of the chosen FP type.
   There is special support for IEEE 754 floating-point and for
   `BigFloat`, otherwise a fallback using `ldexp` is used.

As a bonus, constructing a `BigFloat` from a `Rational` should now be
thread-safe when the rounding mode and precision are provided to the
constructor, because there is no access to the global precision or
rounding mode settings.

Updates JuliaLang#45213

Updates JuliaLang#50940

Updates JuliaLang#52507

Fixes JuliaLang#52394

Closes JuliaLang#52395

Fixes JuliaLang#52859
nsajko added a commit to nsajko/julia that referenced this pull request Jan 14, 2024
@nsajko
Base: make constructing a float from a rational exact
983c27a 
Implementation approach:

1. Convert the (numerator, denominator) pair to a (sign bit, integral
   significand, exponent) triplet using integer arithmetic. The integer
   type in question must be wide enough.

2. Convert the above triplet into an instance of the chosen FP type.
   There is special support for IEEE 754 floating-point and for
   `BigFloat`, otherwise a fallback using `ldexp` is used.

As a bonus, constructing a `BigFloat` from a `Rational` should now be
thread-safe when the rounding mode and precision are provided to the
constructor, because there is no access to the global precision or
rounding mode settings.

Updates JuliaLang#45213

Updates JuliaLang#50940

Updates JuliaLang#52507

Fixes JuliaLang#52394

Closes JuliaLang#52395

Fixes JuliaLang#52859
nsajko added a commit to nsajko/julia that referenced this pull request Jan 15, 2024
@nsajko
Base: make constructing a float from a rational exact
8fad4a7 
Implementation approach:

1. Convert the (numerator, denominator) pair to a (sign bit, integral
   significand, exponent) triplet using integer arithmetic. The integer
   type in question must be wide enough.

2. Convert the above triplet into an instance of the chosen FP type.
   There is special support for IEEE 754 floating-point and for
   `BigFloat`, otherwise a fallback using `ldexp` is used.

As a bonus, constructing a `BigFloat` from a `Rational` should now be
thread-safe when the rounding mode and precision are provided to the
constructor, because there is no access to the global precision or
rounding mode settings.

Updates JuliaLang#45213

Updates JuliaLang#50940

Updates JuliaLang#52507

Fixes JuliaLang#52394

Closes JuliaLang#52395

Fixes JuliaLang#52859
nsajko added a commit to nsajko/julia that referenced this pull request Jan 15, 2024
@nsajko
Base: correctly rounded floats constructed from rationals
314db19 
Constructing a floating-point number from a `Rational` should now be
correctly rounded.

Implementation approach:

1. Convert the (numerator, denominator) pair to a (sign bit, integral
   significand, exponent) triplet using integer arithmetic. The integer
   type in question must be wide enough.

2. Convert the above triplet into an instance of the chosen FP type.
   There is special support for IEEE 754 floating-point and for
   `BigFloat`, otherwise a fallback using `ldexp` is used.

As a bonus, constructing a `BigFloat` from a `Rational` should now be
thread-safe when the rounding mode and precision are provided to the
constructor, because there is no access to the global precision or
rounding mode settings.

Updates JuliaLang#45213

Updates JuliaLang#50940

Updates JuliaLang#52507

Fixes JuliaLang#52394

Closes JuliaLang#52395

Fixes JuliaLang#52859
nsajko added a commit to nsajko/julia that referenced this pull request Jan 15, 2024
@nsajko
Base: correctly rounded floats constructed from rationals
8665610 
Constructing a floating-point number from a `Rational` should now be
correctly rounded.

Implementation approach:

1. Convert the (numerator, denominator) pair to a (sign bit, integral
   significand, exponent) triplet using integer arithmetic. The integer
   type in question must be wide enough.

2. Convert the above triplet into an instance of the chosen FP type.
   There is special support for IEEE 754 floating-point and for
   `BigFloat`, otherwise a fallback using `ldexp` is used.

As a bonus, constructing a `BigFloat` from a `Rational` should now be
thread-safe when the rounding mode and precision are provided to the
constructor, because there is no access to the global precision or
rounding mode settings.

Updates JuliaLang#45213

Updates JuliaLang#50940

Updates JuliaLang#52507

Fixes JuliaLang#52394

Closes JuliaLang#52395

Fixes JuliaLang#52859
@vtjnash
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vtjnash commented Feb 6, 2024 

numbers                                          (12) |         failed at 2024-01-13T01:37:41.184
2024-01-12 20:37:41 EST	Test Failed at /cache/build/tester-amdci4-15/julialang/julia-master/julia-770900211a/share/julia/test/numbers.jl:2929
2024-01-12 20:37:41 EST	  Expression: all((m->begin
2024-01-12 20:37:41 EST	            #= /cache/build/tester-amdci4-15/julialang/julia-master/julia-770900211a/share/julia/test/numbers.jl:2929 =#
2024-01-12 20:37:41 EST	            m.file === Symbol("deprecated.jl")
2024-01-12 20:37:41 EST	        end), (collect(methods(T)))[findall((R->(#= /cache/build/tester-amdci4-15/julialang/julia-master/julia-770900211a/share/julia/test/numbers.jl:2930 =#
2024-01-12 20:37:41 EST	                    !(R <: T))), Base.return_types(T))])
2024-01-12 20:37:41 EST

Seems like there may be an inference issue. Maybe @oscardssmith can help get this finished though, since it seems a good performance improvement?

Also, might want to sprinkle around some GC.@preserve near the unsafe load/store calls just to be careful.

@inkydragon inkydragon added the domain:bignums BigInt and BigFloat label Feb 6, 2024
@hycakir
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hycakir commented Feb 28, 2024

Where would I need GC.@preserve? It seems all calls to unsafe_store makes explicit use of the relevant objects. GC should not collect these objects, no?

@nsajko nsajko added the performance Must go faster label Feb 29, 2024
nsajko added a commit to nsajko/julia that referenced this pull request May 12, 2024
@nsajko
Base: correctly rounded floats constructed from rationals
5639ac6 
Constructing a floating-point number from a `Rational` should now be
correctly rounded.

Implementation approach:

1. Convert the (numerator, denominator) pair to a (sign bit, integral
   significand, exponent) triplet using integer arithmetic. The integer
   type in question must be wide enough.

2. Convert the above triplet into an instance of the chosen FP type.
   There is special support for IEEE 754 floating-point and for
   `BigFloat`, otherwise a fallback using `ldexp` is used.

As a bonus, constructing a `BigFloat` from a `Rational` should now be
thread-safe when the rounding mode and precision are provided to the
constructor, because there is no access to the global precision or
rounding mode settings.

Updates JuliaLang#45213

Updates JuliaLang#50940

Updates JuliaLang#52507

Fixes JuliaLang#52394

Closes JuliaLang#52395

Fixes JuliaLang#52859
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