Add basis_fits_in_grid function

src/Basis.C

@@ -136,6 +136,14 @@ bool Basis::factorizable(int n) const
 int Basis::np(int i) const { return np_[i]; }
 
 ////////////////////////////////////////////////////////////////////////////////
+bool Basis::fits_in_grid(int np0, int np1, int np2) const
+{ return
+  ( idxmax_[0] < np0/2 ) && ( idxmin_[0] >= -np0/2 ) &&
+  ( idxmax_[1] < np1/2 ) && ( idxmin_[1] >= -np1/2 ) &&
+  ( idxmax_[2] < np2/2 ) && ( idxmin_[2] >= -np2/2 );
+}
+
+////////////////////////////////////////////////////////////////////////////////
 const D3vector Basis::kpoint(void) const { return kpoint_; }
 
 ////////////////////////////////////////////////////////////////////////////////

src/Basis.h

@@ -80,6 +80,7 @@ class Basis
   const UnitCell& refcell() const;// reference cell dimensions
   const D3vector kpoint() const; // k-point in units of b0,b1,b2
   int np(int i) const;           // good size of FFT grid in direction i
+  bool fits_in_grid(int np0, int np1, int np2) const;
   bool factorizable(int n) const;// check if n is factorizable with low factors
   int idxmin(int i) const;       // smallest index in direction i
   int idxmax(int i) const;       // largest index in direction i

src/FourierTransform.C

@@ -248,6 +248,10 @@ FourierTransform::FourierTransform (const Basis &basis,
     rdispl[iproc] = rdispl[iproc-1] + rcounts[iproc-1];
   }
 
+  // check if the basis_ fits in the grid np0, np1, np2
+  basis_fits_in_grid_ = basis_.fits_in_grid(np0,np1,np2);
+  assert(basis_fits_in_grid_);
+
   if ( basis_.real() )
   {
     // compute index arrays ifftp_ and ifftm_ for mapping vector->zvec

src/FourierTransform.h

@@ -65,6 +65,7 @@ class FourierTransform
   int ntrans0_,ntrans1_,ntrans2_;
 
   int nvec_;
+  bool basis_fits_in_grid_;
 
   std::vector<int> np2_loc_; // np2_loc_[iproc], iproc=0, nprocs_-1
   std::vector<int> np2_first_; // np2_first_[iproc], iproc=0, nprocs_-1