Jungfraujoch/image_analysis/structure_refinement/ModelGrid.h

// SPDX-FileCopyrightText: 2026 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
// SPDX-License-Identifier: GPL-3.0-only

#pragma once

#include <cstddef>
#include <vector>

#include "gemmi/dencalc.hpp"   // DensityCalculator
#include "gemmi/grid.hpp"
#include "gemmi/it92.hpp"      // IT92 x-ray form factors
#include "gemmi/model.hpp"

// gemmi's gridding of a model - the density of DensityCalculator::put_model_density_on_grid() and the
// bulk-solvent mask of SolventMasker(AtomicRadiiSet::Refmac).put_mask_on_grid() - spread over
// `nthreads` threads of ParallelFor's pool. Every grid point receives the same operations in the same
// order as in gemmi's serial loops, so the grids are the same on any number of threads: the mask is gemmi's
// bit for bit, the density gemmi's but for the last bits (its points are placed in single precision, as the
// Apple GPU places them).

// The points gemmi's Grid::symmetrize() reduces the orbits of this grid's size and space group into
// (empty in P1). Both functions below take them, for a grid of the same size.
std::vector<size_t> OrbitLeaders(const gemmi::Grid<float> &grid, size_t nthreads);

// `dc` set up as for put_model_density_on_grid(): d_min, rate, blur, the grid's cell and group. On macOS the
// Apple GPU puts the density on the grid (ModelDensityMetal.h), to the same bits; `gpu` false keeps it on the
// CPU.
void PutModelDensityOnGrid(gemmi::DensityCalculator<gemmi::IT92<float>, float> &dc, const gemmi::Model &model,
                           const std::vector<size_t> &orbit_leaders, size_t nthreads, bool gpu = true);

// `grid` sized, with its cell and group set.
void PutMaskOnGrid(gemmi::Grid<float> &grid, const gemmi::Model &model, const std::vector<size_t> &orbit_leaders,
                   size_t nthreads);

// The number of points of the grid a model's structure factors to d_min are computed on at DensityCalculator's
// `rate` (a spacing of d_min / (2 rate)) in this cell and space group: the grid's size, without making it.
size_t ModelGridPoints(const gemmi::UnitCell &cell, const gemmi::SpaceGroup *sg, double d_min, double rate = 1.5);

// What computing a model's structure factors on the CPU holds at its peak, per point of that grid: the density
// and the bulk-solvent mask grids, and for each of them its transform's input copy, spectrum and coefficients,
// with the two made at once (ModelValidation's compute_model_factors).
constexpr size_t MODEL_FACTORS_BYTES_PER_GRID_POINT = 32;
// What a molecular-replacement placement's structure factors and rigid body hold on the CPU at their peak, per
// point of that grid: measured at under half of the above.
constexpr size_t MODEL_PLACEMENT_BYTES_PER_GRID_POINT = 16;