BRepLib_ValidateEdge aBRepLib_ValidateEdgeOnClosedSurface(myHCurve, ACS, SameParameter);
              
aBRepLib_ValidateEdge.SetExactMathod(Standard_False);
              aBRepLib_ValidateEdge.SetExitIfToleranceExceeded(Tol);
              aBRepLib_ValidateEdgeOnClosedSurface.Process();
              if (!aBRepLib_ValidateEdge.IsDone() || !aBRepLib_ValidateEdgeOnClosedSurface.CheckTolerance(Tol))

isTheMultyTheradDisabled

  const Handle(Adaptor3d_Curve) anAdaptor3dCurve = new BRepAdaptor_Curve(theEdge, theFace);

  const Handle(Geom_Curve)& aC3dTmp = BRep_Tool::Curve(theEdge, aLocation, aFirstCurveOnSurfaceParam, 
aLastCurveOnSurfaceParam);

  Handle(Geom_Surface) aTransformedGeomSurface = Handle(Geom_Surface)::
    DownCast(aGeomSurface->Transformed(aLocation.Transformation()));

     BRep_Tool::CurveOnSurface(TopoDS::Edge(theEdge.Reversed()), aGeom2dReversedCurve, aGeomSurface2, 
                               
aLocation2, aFirstReverseParam, aLastReverseParam);
     Handle(Geom_Surface) aTransformedGeomSurface2 = Handle(Geom_Surface)::
       DownCast(aGeomSurface2->Transformed(aLocation2.Transformation()));

     Handle(GeomAdaptor_Surface) aGeomAdaptorReversedSurface = new GeomAdaptor_Surface(aGeomSurface2);

//! Computes the max distance between 3D-curve and curve on 
//! surface in fixed points number

  //! using exact method alwais computes real max distance.

  Standard_Integer myContrloPointsNumber; 

//=============================================================================
//function : CorrectTolerance
//purpose  : 
//=============================================================================
void BRepLib_ValidateEdge::UpdateTolerance(Standard_Real& theToleranceToUpdate)

      if (myExitIfToleranceExceeded && aMaxSquareDistance > aSquareToleranceForChecking)
      
{
        return;
      }

  const Handle(Adaptor3d_Curve) aGeomAdaptorCurve = new GeomAdaptor_Curve(theCurve3D);

          BRepLib_ValidateEdge aBRepLib_ValidateEdgeOnClosedSurface(myHCurve, ACS, SameParameter);
          aBRepLib_ValidateEdgeOnClosedSurface.Process();
          aBRepLib_ValidateEdgeOnClosedSurface.UpdateTolerance(aNewTolerance);
          if (aBRepLib_ValidateEdge.IsDone() && !aBRepLib_ValidateEdgeOnClosedSurface.CheckTolerance(Tol))

    Handle(Geom_Surface) aGeomSurface2;
    TopLoc_Location aLocation2;

  Standard_EXPORT void SetContrloPointsNumber(Standard_Integer theContrloPointsNumber)
  {
    myContrlPointsNumber = theContrloPointsNumber;
  }
...
  Standard_Integer myContrlPointsNumber; 

#include <BRepLib.hxx>

    BRepLib_ValidateEdge aBRepLib_ValidateEdge(aCurve3d, aCurveOnSurf, Standard_True);

    Standard_Real aMaxTol1 = aBRepLib_ValidateEdge.GetMaxDistance();

    BRepLib_ValidateEdge aBRepLib_ValidateEdge(aGAC, ACS, SameParameter);

      BRepLib_ValidateEdge aBRepLib_ValidateEdge(aGAC, ACS, Standard_True);

  //! Sets limit to compute a distance in the Process() function. If the distance greater than 
  //! theToleranceForChecking the Process() function stopped. Use this in case checking of 
  //! tolerance for best performcnce

  //! Sets the maximal allowed distance in the Process() function. If the distance greater than 
  //! theToleranceForChecking the Process() function stops. Use this for best performance 
  //! in case of checking of tolerance.

  //!  function was called before <myCalculatedDistance> containts first 

  //! Returns true if compute distance less than <theToleranceToCheck>

  //! Increace <theToleranceToUpdate> if max distance is greater than <theToleranceToUpdate>

  Standard_Real aCurvePrecition = BRepCheck::PrecCurve(*myReferenceCurve);
  Standard_Real aSurfacePrecition = BRepCheck::PrecSurface(aSurface);

        myCalculatedDistance = sqrt(aMaxSquareDistance);

Add new class BRepLib_ValidateEdge to edge checking to use instead function:

Add new class BRepLib_ValidateEdge to use for edge checking instead of functions:

--- /dev/null
+++ b/src/BRepLib/BRepLib_ValidateEdge.cxx
...
+
+
+#include <Adaptor3d_Curve.hxx>
+#include <Adaptor3d_CurveOnSurface.hxx>
+#include <BRepCheck.hxx>
+#include <BRepLib_ValidateEdge.hxx>

+  Standard_EXPORT void SetControlPointsNumber(Standard_Integer theControlPointsNumber)
+  {
+    myControlPointsNumber = theControlPointsNumber;
+  }
...
+  Standard_EXPORT Standard_Boolean IsDone()
+  {
+    return myIsDone;
+  }
...
?

+private:
+  //! Adds some margin for distance checking
+  Standard_Real CorrectTolerance(Standard_Real theTolerance);
+
+  Handle(Adaptor3d_Curve) myReferenceCurve;

- const Standard_Boolean isTheMultyTheradDisabled = Standard_False);
+ const Standard_Boolean isMultyThread = Standard_True);

  aCS.Perform (theCurve2D, !theToRunParallel);