Bad behaviour with Rump sum

[Olivier Cessenat]

I'm having an issue with Rump sum which I wrote with your help at école d'été 2018
srump.f90.gz
I get wrong results

$ gfortran  -mieee-fp -mno-fma srump.f90 -o a.srump && ./a.srump
 s=   33554432.0      0.471077561       6.02297187E-02
 snaive=   16777216.0    
 s16=   499858460.940718650817871093750000000      
$ ifort -fp-model strict srump.f90 -o a.srump && ./a.srump
 s=  3.3554432E+07  3.9208680E-07  0.6640171    
 snaive=  1.6777216E+07
 s16=   499869302.874310873448848724365234      

What did I do wrong ?
Can you help @ffevotte ?
Thanks