Hello, 

So assume I have 140K variables of the form y_ijkl. These are binary variables and represent order between 2 jobs on a single machine. 

I need to write 140K*2 = 280K constraints of the form:

s_ik + d_ik <= s_jl + M(1-y_ijkl)  ->(1)
s_jl + d_jl  <= s_ik + M*y_ijkl  -->(2)

So 140K constraints of type 1 and another 140K of type2. 

Is there any way I can make the addition of these constraints much faster. ?
I am sure there are ways to do it. There is some structure or method I am not employing.

Thanks
Hariharan

What interface are you using ? 
In docplex (Python) you can improve constraint addition by adding blocks of constraints using add_constraints() instead of adding them one by one. 
An example of usage is in the example workflow/lagrangian_relaxation.py : 
https://github.com/IBMDecisionOptimization/docplex-examples/blob/master/examples/mp/workflow/lagrangian_relaxation.py

Regards,

Philippe