using LinearAlgebra

struct ValueOne; end
ValueOne()

# Compute X <- a X + b I.
function matfun_axpby!(X,a,b,Y::UniformScaling)
    m,n=size(X)
    if ~(a isa ValueOne)
        rmul!(X,a)
    end
    @inbounds for i=1:n
        X[i,i]+=(b isa ValueOne) ? 1 : b
    end
end

@inline function exp_sastre_m6_opt_rho2_7(A)
    T=promote_type(eltype(A),Float64)
    A_copy=similar(A,T); A_copy .= A;
    return exp_sastre_m6_opt_rho2_7!(A_copy)
end

@inline function exp_sastre_m6_opt_rho2_7!(A)
    T=promote_type(eltype(A),Float64) # Make it work for many 'bigger' types (matrices and scalars)
    # max_memslots=9
    n=size(A,1)
    # The first slots are precomputed nodes [:A]
    memslots2 = similar(A,T)
    memslots3 = similar(A,T)
    memslots4 = similar(A,T)
    memslots5 = similar(A,T)
    memslots6 = similar(A,T)
    memslots7 = similar(A,T)
    memslots8 = similar(A,T)
    memslots9 = similar(A,T)
    # Assign precomputed nodes memslots 
    memslots1=A # overwrite A
    # Uniform scaling is exploited.
    # No matrix I explicitly allocated.
    # Computation order: Bb2 Ba2 B2 Ba3 Bb3 B3 Ba4 Bb4 B4 Ba5 Bb5 B5 Ba6 Bb6 B6 Ba7 Bb7 B7 T2k9
    # Computing Bb2 = x*I+x*A
    coeff1=0.0014414740602762641
    coeff2=1.015909177999167
    memslots2 .= coeff2.*memslots1
    mul!(memslots2,true,I*coeff1,true,true)
    # Computing Ba2 = x*I+x*A
    coeff1=0.0014414740602762641
    coeff2=1.015909177999167
    memslots3 .= coeff2.*memslots1
    mul!(memslots3,true,I*coeff1,true,true)
    # Computing B2 with operation: mult
    mul!(memslots4,memslots3,memslots2)
    # Deallocating Ba2 in slot 3
    # Deallocating Bb2 in slot 2
    # Computing Ba3 = x*I+x*A+x*B2
    coeff1=0.00203407200644078
    coeff2=-0.004855370488778173
    coeff3=1.0000472141119134
    memslots2 .= coeff2.*memslots1 .+ coeff3.*memslots4
    mul!(memslots2,true,I*coeff1,true,true)
    # Computing Bb3 = x*I+x*A+x*B2
    coeff1=-0.0068121857554928915
    coeff2=0.0018059085648684517
    coeff3=0.00010342034415488765
    memslots3 .= coeff2.*memslots1 .+ coeff3.*memslots4
    mul!(memslots3,true,I*coeff1,true,true)
    # Computing B3 with operation: mult
    mul!(memslots5,memslots2,memslots3)
    # Deallocating Ba3 in slot 2
    # Deallocating Bb3 in slot 3
    # Computing Ba4 = x*I+x*A+x*B2+x*B3
    coeff1=-0.00216500404580565
    coeff2=0.09646644408880453
    coeff3=0.014294207683808999
    coeff4=1.1172277610690486
    memslots2 .= coeff2.*memslots1 .+ coeff3.*memslots4 .+ coeff4.*memslots5
    mul!(memslots2,true,I*coeff1,true,true)
    # Computing Bb4 = x*I+x*A+x*B2+x*B3
    coeff1=-0.029613578842783986
    coeff2=0.377669985575162
    coeff3=0.05304182885989784
    coeff4=1.022330965215494
    memslots3 .= coeff2.*memslots1 .+ coeff3.*memslots4 .+ coeff4.*memslots5
    mul!(memslots3,true,I*coeff1,true,true)
    # Computing B4 with operation: mult
    mul!(memslots6,memslots2,memslots3)
    # Deallocating Ba4 in slot 2
    # Deallocating Bb4 in slot 3
    # Computing Ba5 = x*I+x*A+x*B2+x*B3+x*B4
    coeff1=-0.0022569437385435
    coeff2=0.0010373403739564698
    coeff3=1.018857479770905
    coeff4=0.02327178284493455
    coeff5=-0.08243100849197117
    memslots2 .= coeff2.*memslots1 .+ coeff3.*memslots4 .+ coeff4.*memslots5 .+ coeff5.*memslots6
    mul!(memslots2,true,I*coeff1,true,true)
    # Computing Bb5 = x*I+x*A+x*B2+x*B3+x*B4
    coeff1=-0.0167704319125257
    coeff2=0.0018989172164601057
    coeff3=7.889567871549961e-5
    coeff4=-0.0009931016008313642
    coeff5=-2.623385669729595e-5
    memslots3 .= coeff2.*memslots1 .+ coeff3.*memslots4 .+ coeff4.*memslots5 .+ coeff5.*memslots6
    mul!(memslots3,true,I*coeff1,true,true)
    # Computing B5 with operation: mult
    mul!(memslots7,memslots2,memslots3)
    # Deallocating Ba5 in slot 2
    # Deallocating Bb5 in slot 3
    # Computing Ba6 = x*I+x*A+x*B2+x*B3+x*B4+x*B5
    coeff1=0.015636244039123465
    coeff2=0.36835598195824903
    coeff3=0.04415666392494207
    coeff4=0.019415313402916037
    coeff5=0.054241015390228235
    coeff6=1.0061285566950167
    memslots2 .= coeff2.*memslots1 .+ coeff3.*memslots4 .+ coeff4.*memslots5 .+ coeff5.*memslots6 .+ coeff6.*memslots7
    mul!(memslots2,true,I*coeff1,true,true)
    # Computing Bb6 = x*I+x*A+x*B2+x*B3+x*B4+x*B5
    coeff1=0.020097851537399642
    coeff2=0.10667353947597173
    coeff3=0.034594555518270974
    coeff4=-0.07438766844651382
    coeff5=0.10144129673946056
    coeff6=0.987202584803334
    memslots3 .= coeff2.*memslots1 .+ coeff3.*memslots4 .+ coeff4.*memslots5 .+ coeff5.*memslots6 .+ coeff6.*memslots7
    mul!(memslots3,true,I*coeff1,true,true)
    # Computing B6 with operation: mult
    mul!(memslots8,memslots2,memslots3)
    # Deallocating Ba6 in slot 2
    # Deallocating Bb6 in slot 3
    # Computing Ba7 = x*I+x*A+x*B2+x*B3+x*B4+x*B5+x*B6
    coeff1=3.1043463304552805
    coeff2=0.7528521412951402
    coeff3=0.159971928559395
    coeff4=7.905233218278997
    coeff5=1.0995871761977756
    coeff6=-0.048631444054980266
    coeff7=0.2841742967744319
    memslots2 .= coeff2.*memslots1 .+ coeff3.*memslots4 .+ coeff4.*memslots5 .+ coeff5.*memslots6 .+ coeff6.*memslots7 .+ coeff7.*memslots8
    mul!(memslots2,true,I*coeff1,true,true)
    # Computing Bb7 = x*I+x*A+x*B2+x*B3+x*B4+x*B5+x*B6
    coeff1=0.008831439952196395
    coeff2=0.29016677501097143
    coeff3=0.07731361344655992
    coeff4=0.01972134822932684
    coeff5=0.2595231983751941
    coeff6=1.9401869208092082
    coeff7=0.9656182105520791
    memslots3 .= coeff2.*memslots1 .+ coeff3.*memslots4 .+ coeff4.*memslots5 .+ coeff5.*memslots6 .+ coeff6.*memslots7 .+ coeff7.*memslots8
    mul!(memslots3,true,I*coeff1,true,true)
    # Computing B7 with operation: mult
    mul!(memslots9,memslots2,memslots3)
    # Deallocating Ba7 in slot 2
    # Deallocating Bb7 in slot 3
    # Computing T2k9 = x*I+x*A+x*B2+x*B3+x*B4+x*B5+x*B6+x*B7
    coeff1=0.9720224032451862
    coeff2=0.08866505998167876
    coeff3=-0.00025013219458514967
    coeff4=0.021251100930175442
    coeff5=-0.13164782415883697
    coeff6=-0.0031660405732008064
    coeff7=0.015815360491620606
    coeff8=0.9769074674369014
    # Smart lincomb recycle A
    memslots1 .= coeff2.*memslots1 .+ coeff3.*memslots4 .+ coeff4.*memslots5 .+ coeff5.*memslots6 .+ coeff6.*memslots7 .+ coeff7.*memslots8 .+ coeff8.*memslots9
    mul!(memslots1,true,I*coeff1,true,true)
    # Deallocating B2 in slot 4
    # Deallocating B3 in slot 5
    # Deallocating B4 in slot 6
    # Deallocating B5 in slot 7
    # Deallocating B6 in slot 8
    # Deallocating B7 in slot 9
    return memslots1 # Returning T2k9
end

