anchor.diff:      exp (- ((x [gp; smpl1] - x [gp; smpl2])**2.0f) / (2.0f * (l [gp])**2.0f) )
   
   [<Fact>]
  +[<Trait("Category", "Skip_CI")>]
   let ``Trace compare: KSE`` () =    
       let nGps = 2
       let nSmpls = 3
  
positive.code:     printfn "dkse / dl=\n%A" dKsedLVal
  
  [<Fact>]
  let ``Eval and deriv: KSE in Expr on CUDA`` () =   
      // input  x[gp, smpl]
      //        l[gp]
  
negative.code:         kse    
      )
  
  [<Fact>]
  [<Trait("Category", "Skip_CI")>]
  let ``Trace compare: dKSE/dX`` () =    
      let nGps = 2
      let nSmpls = 3
  