fixed bug in fiber texture component caused non-even distribution by correctly getting numbers of the halton sequence

code/math.f90

@@ -937,6 +937,7 @@ pure subroutine Gauss (dimen,A,B,LogAbsDetA,NegHDK,error)
 
  implicit none
 
+
  logical, intent(out) :: error
  integer(pInt), intent(in) :: dimen
  integer(pInt), intent(out) :: NegHDK
@@ -1062,6 +1063,7 @@ pure subroutine Gauss (dimen,A,B,LogAbsDetA,NegHDK,error)
     LogAbsDetA = LogAbsDetA + LOG10(AbsA)
  ENDDO
 
+
  error = .false.
 
 end subroutine Gauss
@@ -1932,16 +1934,16 @@ endif
 end function math_sampleGaussOri
  
 
-!********************************************************************
+!--------------------------------------------------------------------------------------------------
-!   draw a random sample from Fiber component
+!> @brief draw a random sample from Fiber component with noise (in radians)
-!   with noise (in radians)
+!--------------------------------------------------------------------------------------------------
-!********************************************************************
 function math_sampleFiberOri(alpha,beta,noise)
 
  implicit none
 
  real(pReal), dimension(3) :: math_sampleFiberOri, fiberInC,fiberInS,axis
- real(pReal), dimension(2) :: alpha,beta, rnd
+ real(pReal), dimension(2), intent(in) :: alpha,beta
+ real(pReal), dimension(6) :: rnd
  real(pReal), dimension(3,3) :: oRot,fRot,pRot
  real(pReal) :: noise, scatter, cos2Scatter, angle
  integer(pInt), dimension(2,3), parameter :: rotMap = reshape((/2_pInt,3_pInt,&
@@ -1974,12 +1976,14 @@ function math_sampleFiberOri(alpha,beta,noise)
  end if
 
 ! ---# rotation matrix about fiber axis (random angle) #---
- call halton(1_pInt,rnd)
+ do
+   call halton(6_pInt,rnd)
    fRot = math_AxisAngleToR(fiberInS,rnd(1)*2.0_pReal*pi)
 
 ! ---# rotation about random axis perpend to fiber #---
 ! random axis pependicular to fiber axis
- call halton(2_pInt,axis)
+
+   axis(1:2) = rnd(2:3)
    if (fiberInS(3) /= 0.0_pReal) then
      axis(3)=-(axis(1)*fiberInS(1)+axis(2)*fiberInS(2))/fiberInS(3)
    else if(fiberInS(2) /= 0.0_pReal) then
@@ -1991,13 +1995,17 @@ function math_sampleFiberOri(alpha,beta,noise)
    end if
 
 ! scattered rotation angle
- do
+   if (noise > 0.0_pReal) then
-   call halton(2_pInt,rnd)
+     angle = acos(cos2Scatter+(1.0_pReal-cos2Scatter)*rnd(4))
-     angle = acos(cos2Scatter+(1.0_pReal-cos2Scatter)*rnd(1))
+     if (rnd(5) <= exp(-1.0_pReal*(angle/scatter)**2.0_pReal)) exit
-     if (rnd(2) <= exp(-1.0_pReal*(angle/scatter)**2.0_pReal)) exit
+   else
+     angle = 0.0_pReal
+     exit
+   end if
  enddo
- call halton(1_pInt,rnd)
+
- if (rnd(1) <= 0.5) angle = -angle
+ if (rnd(6) <= 0.5) angle = -angle
+ 
  pRot = math_AxisAngleToR(axis,angle)
 
 ! ---# apply the three rotations #---
@@ -3646,6 +3654,7 @@ if (pReal /= C_DOUBLE .or. pInt /= C_INT) call IO_error(error_ID=808_pInt)
 end subroutine divergence_fft
 
 
+          
 !+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 
 subroutine divergence_fdm(res,geomdim,vec_tens,order,field,divergence)
 !+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
@@ -3711,6 +3720,7 @@ subroutine divergence_fdm(res,geomdim,vec_tens,order,field,divergence)
 end subroutine divergence_fdm
 #endif
 
+
 !+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 
 subroutine tensor_avg(res,tensor,avg)
 !+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++