SAS decimal precision and writing to database - sas

Question

Good day,
I had this issue where I was writing some numbers to database, which should have had value 0.1 in SAS, but for some bizarre reason appeared as 0.09 in SQL database. When I manually checked the dataset it showed 0.10 in format 12.2.
So what I do is check if the values are actually 0.1 or somewhat below this:
data _checking;
set publish_data;
if value < 0.1;
dummy = value*10000000;
run;
It appeared that number of observations fulfill the first condition. Ok... That explains why the values come out as 0.09. Rounding issue.
However, all dummy values come out as integers. I tried 10, 100, 1k, 10k all appear to come out as integers. (1, 10, 100 ...)
Next step I try:
data _checking2;
set _checking;
if dummy<10; /*Depending on the factorial*/
run;
This is consistent. Dummy retains the value 'a little below the value shown'.
I solved the issue by round(value,.1);
Questions:
How to observe the actual value stored in dataset? (Especially in case 'a little below')
If first condition if is true, then how can the checking with dummy still show integer values. (Because in computers epsilon has to have actual value)
2.b Or is this just a display issue? Or does SAS has flag for 'value minus epsilon'?

Answer 1

Answer 1:
The most precise and least human way to see the actual value is to observe the underlying IEEE bytes using HEX format.
Answer 2:
The default format for those new dummy variables is BEST12., so you won't see any small offsets if they are smaller than what best12. will show, or more precisely epsilon < 1e-(12-log10(x)). The SAS format could be considered a display issue in this case.
If your use case is that of a 'shown' value must be the actual value sent to a remote database then you will want to use ROUND prior to populating the remote tables.
data x;
x = 1/3; output;
x = 0.1 - 1e-13; output;
format x 12.2;
run;
data y;
set x;
put x= x= HEX16.;
xhex = x;
format xhex hex16.;
array dummy dummy1-dummy13;
do _n_ = 1 to 13;
dummy(_n_) = x * 10**_n_;
end;
run;
proc print data=y;
run;
data z;
do p = 0 to 10;
do q = 1 to 15;
array z z1-z15;
z(q) = 10**p + 10**-q;
end; output;
end;
drop p q;
run;
==== LOG ====
x=0.33 x=3FD5555555555555
x=0.10 x=3FB9999999997D74
==== PRINT ====
Obs x xhex dummy1 dummy2 dummy3 dummy4 dummy5 dummy6 dummy7
1 0.33 3FD5555555555555 3.33333 33.3333 333.333 3333.33 33333.33 333333.33 3333333.33
2 0.10 3FB9999999997D74 1.00000 10.0000 100.000 1000.00 10000.00 100000.00 1000000.00
Obs dummy8 dummy9 dummy10 dummy11 dummy12 dummy13
1 33333333.33 333333333.33 3333333333.3 33333333333 333333333333 3.3333333E12
2 10000000.00 100000000.00 1000000000.0 10000000000 100000000000 999999999999

Answer 2

You can try a different format. try 32.31 or best32.
Subtract 0.1-value and look at the result. Again, use a format with a lot of decimal places.
You are probably not seeing the value in the dummy variables because the epsilon is very small and the dummy is still getting rounded for display.
Try dummy=value*1e16 or higher.
Numbers in SAS are C doubles, fwiw.