[petsc-users] set shift while not setting target

[Denis Davydov]

Dear all, 

What is the expected behaviour when a user set shift value via STSetShift() with shift or shift-and-invert transformations, 
but ignores setting target via EPSSetTarget ? 

From the Table 2.2 (chapter 2.3), it seems that Target are used only in conjunction with EPS_TARGET_XXX of EPSWhich. 
Even though it is written in chapter 3.3 that "In all transformations except STSHIFT, there is a direct connection between the target τ (described in §2.3) and the shift σ, as will be discussed below.”
it does not look like the absence of EPSSetTarget call would affect solution with ST objects. 
At least that is my experience so far at least with Slepc 3.5.3.

p.s. Of course, there is a logical connecting, namely one obtains eigenvalues near the shift value. 
p.p.s. I am solving GHEP for EPS_SMALLEST_REAL.

Kind regards,
Denis