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Optimized gamma. Was: Saving gamma: Base._fact_table64 is dangerous #142

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Optimized gamma. Was: Saving gamma: Base._fact_table64 is dangerous #142

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34769d7
Saving gamma: Base._fact_table64 is dangerous
PallHaraldsson Jan 10, 2019
0cb30fc
Need to widen it seems for 32-bit; optimization
PallHaraldsson Jan 10, 2019
06bc136
The optimization wasn't right
PallHaraldsson Jan 10, 2019
c127a0e
Better optimization to not widen this much
PallHaraldsson Jan 10, 2019
f8d40b6
Correct value for fast path.
PallHaraldsson Jan 10, 2019
277665e
More readable, and you still be as fast; faster
PallHaraldsson Jan 18, 2019
e250b09
Better range and corrected the name!
PallHaraldsson Jan 20, 2019
5100a08
Still correct, and should be faster with other PR
PallHaraldsson Jan 20, 2019
d7e621c
More optimized with table and fixes 32-bit
PallHaraldsson Jan 20, 2019
5f54476
Fix
PallHaraldsson Jan 20, 2019
ecbfe8a
Now correct fix...
PallHaraldsson Jan 20, 2019
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17 changes: 9 additions & 8 deletions src/gamma.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -748,14 +748,15 @@ if Base.MPFR.version() >= v"4.0.0"
end
end

## from base/combinatorics.jl'

function gamma(n::Union{Int8,UInt8,Int16,UInt16,Int32,UInt32,Int64,UInt64})
n < 0 && throw(DomainError(n, "`n` must not be negative."))
n == 0 && return Inf
n <= 2 && return 1.0
n > 20 && return gamma(Float64(n))
@inbounds return Float64(Base._fact_table64[n-1])
const _shifted_gamma_fact_table = [Inf; gamma.(collect(1.0:171.0))]

function gamma(n::Union{Int8,UInt8,Int16,UInt16,Int32,UInt32,Int64,UInt64,Int128,UInt128})
if !(0 <= n <= 171)
0 <= n && return Inf
else
return @inbounds _shifted_gamma_fact_table[(n+1)]
end
throw(DomainError(n, "`n` must not be negative."))
end

## from base/math.jl
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