Merge pull request #359 from NNPDF/capi-set-subgrid

Add `set_subgrid` interface to the C-API

Author: Radonirinaunimi

examples/cpp/Makefile

@@ -14,6 +14,7 @@ PROGRAMS = \
 	convolve-grid-deprecated \
 	convolve-grid \
 	get-subgrids \
+	set-subgrids \
 	evolve-grid \
 	evolve-grid-identity \
 	deprecated \
@@ -57,6 +58,9 @@ deprecated: deprecated.cpp
 get-subgrids: get-subgrids.cpp
 	$(CXX) $(CXXFLAGS) $< $(PINEAPPL_DEPS) -o $@
 
+set-subgrids: set-subgrids.cpp
+	$(CXX) $(CXXFLAGS) $< $(PINEAPPL_DEPS) -o $@
+
 evolve-grid: evolve-grid.cpp
 	$(CXX) $(CXXFLAGS) $< $(LHAPDF_DEPS) $(PINEAPPL_DEPS) -o $@
 

examples/cpp/set-subgrids.cpp

@@ -0,0 +1,221 @@
+#include <cstdint>
+#include <pineappl_capi.h>
+
+#include <cassert>
+#include <cmath>
+#include <cstddef>
+#include <iostream>
+#include <random>
+#include <string>
+#include <tuple>
+#include <vector>
+
+using KinematicsTuple = std::tuple<double, double, double>;
+
+struct KinInterpolation {
+    std::vector<double> x_interp;
+    std::vector<double> z_interp;
+};
+
+template<typename T>
+std::vector<T> geomspace(T start, T stop, int num, bool endpoint = false) {
+    std::vector<T> result(num);
+
+    if (num == 1) {
+        result[0] = start;
+        return result;
+    }
+
+    T log_start = std::log(start);
+    T log_stop = std::log(stop);
+    T step = (log_stop - log_start) / (endpoint ? (num - 1) : num);
+
+    for (int i = 0; i < num; ++i) {
+        result[i] = std::exp(log_start + i * step);
+    }
+
+    return result;
+}
+
+KinInterpolation kinematics_interpolation_points() {
+    std::vector<double> x = geomspace(1e-5, 1.0, 50);
+    std::vector<double> z = geomspace(1e-5, 1.0, 50);
+
+    return {x, x};
+}
+
+std::vector<double> generate_subgrid_arrays(
+    std::mt19937& rng,
+    std::vector<double> x,
+    std::vector<double> z
+) {
+    std::size_t kin_length = x.size() * z.size();
+    std::vector<double> subgrid(kin_length);
+
+    // NOTE: `subgrid` is a flatten matrix whose layout was `[q2=1][x][z]`.
+    // The order of the kinematics shoud match the kinematics declaration.
+    for (std::size_t i = 0; i != kin_length; i++) {
+        subgrid[i] = std::generate_canonical<double, 53>(rng);
+    }
+
+    return subgrid;
+}
+
+void fill_grid(pineappl_grid* grid, std::vector<KinematicsTuple> kin_tuples) {
+    auto rng = std::mt19937();
+
+    auto* channels = pineappl_grid_channels(grid);
+    std::size_t n_bins = pineappl_grid_bin_count(grid);
+    std::size_t n_orders = pineappl_grid_order_count(grid);
+    std::size_t n_channels = pineappl_channels_count(channels);
+
+    // Get the kinematics
+    KinInterpolation kins = kinematics_interpolation_points();
+    std::vector<double> x_interp = kins.x_interp;
+    std::vector<double> z_interp = kins.z_interp;
+
+    // Extract the shape of the subgrid - Q2 always passed as an array of ONE element
+    std::vector<std::size_t> subgrid_shape = {1, x_interp.size(), z_interp.size()};
+
+    for (std::size_t b = 0; b != n_bins; b++) {
+        for (std::size_t o = 0; o != n_orders; o++) {
+            for (std::size_t c = 0; c != n_channels; c++) {
+                // Construct the node values of {Q2, x_inter, z_interp}
+                // NOTE: Pay attention to the order, it should match the kinematics declaration
+                // and how the subgrid was constructed (see `generate_subgrid_array`).
+                std::vector<double> node_values = { std::get<0>(kin_tuples[b]) };
+                node_values.insert(node_values.end(), x_interp.begin(), x_interp.end());
+                node_values.insert(node_values.end(), z_interp.begin(), z_interp.end());
+
+                // Mock the subgrids for a given bin, order, and channel
+                std::vector<double> subgrid_arrays = generate_subgrid_arrays(rng, x_interp, z_interp);
+
+                // set the subgrids
+                pineappl_grid_set_subgrid(
+                    grid,
+                    b, o, c, // kinematics index
+                    node_values.data(),
+                    subgrid_arrays.data(),
+                    subgrid_shape.data()
+                );
+            }
+        }
+    }
+
+    // Remove channels object from memory
+    pineappl_channels_delete(channels);
+}
+
+int main() {
+    // ---
+    // Create all channels
+
+    std::size_t nb_convolutions = 2;
+    auto* channels = pineappl_channels_new(nb_convolutions);
+
+    int32_t pids1[] = { 21, 21 };
+    double factors1[] = { 1.0 };
+    // define the channel #0
+    pineappl_channels_add(channels, 1, pids1, factors1);
+
+    // create another channel this channel is the down-type-antidown-type quark channel; here we
+    int32_t pids2[] = { 1, -1, 3, -3, 5, -5 };
+    // define the channel #1
+    pineappl_channels_add(channels, 3, pids2, nullptr);
+
+    // ---
+    // Specify the perturbative orders that will be filled into the grid
+    std::vector<uint8_t> orders = {
+        1, 0, 0, 0, 0, // order #0: LO QCD
+        2, 0, 0, 0, 0, // order #1: NLO QCD
+    };
+
+    // ---
+    // Specify the bin limits
+
+    // In SIDIS, a bin is defined as a tuple (Q2, x, z) values (3D).
+    std::vector<KinematicsTuple> kin_obs = {std::make_tuple(1e3, 1e-5, 1e-2), std::make_tuple(1e4, 1e-2, 1e-3)};
+    // We are going to define some placeholder 1D bins that we'll overwrite later.
+    std::vector<double> bins;
+    for (std::size_t i = 0; i < kin_obs.size() + 1; ++i) {
+        bins.push_back(static_cast<float>(i));
+    }
+
+    // ---
+    // Construct the objects that are needed to fill the Grid
+
+    pineappl_pid_basis pid_basis = PINEAPPL_PID_BASIS_EVOL;
+    pineappl_conv convs[] = {
+        { PINEAPPL_CONV_TYPE_UNPOL_PDF, 2212 },
+        { PINEAPPL_CONV_TYPE_UNPOL_FF, 211 }, // Assumes Pion
+    };
+
+    // Define the kinematics required for this process. In the following example we have ONE single
+    // scale and two momentum fractions (corresponding to the two initial- and final-state hadrons).
+    // The format of the kinematics is: { type, value }.
+    pineappl_kinematics scales = { PINEAPPL_KINEMATICS_SCALE, 0 };
+    pineappl_kinematics x1 = { PINEAPPL_KINEMATICS_X, 0 };
+    pineappl_kinematics x2 = { PINEAPPL_KINEMATICS_X, 1 };
+    pineappl_kinematics kinematics[3] = { scales, x1, x2 };
+
+    // Define the specificities of the interpolations for each of the kinematic variables.
+    pineappl_reweight_meth scales_reweight = PINEAPPL_REWEIGHT_METH_NO_REWEIGHT; // Reweighting method
+    pineappl_reweight_meth moment_reweight = PINEAPPL_REWEIGHT_METH_APPL_GRID_X;
+    pineappl_map scales_mapping = PINEAPPL_MAP_APPL_GRID_H0; // Mapping method
+    pineappl_map moment_mapping = PINEAPPL_MAP_APPL_GRID_F2;
+    pineappl_interp_meth interpolation_meth = PINEAPPL_INTERP_METH_LAGRANGE;
+    pineappl_interp interpolations[3] = {
+        { 1e2, 1e8, 40, 3, scales_reweight, scales_mapping, interpolation_meth },  // Interpolation fo `scales`
+        { 2e-7, 1.0, 50, 3, moment_reweight, moment_mapping, interpolation_meth }, // Interpolation fo `x1`
+        { 2e-7, 1.0, 50, 3, moment_reweight, moment_mapping, interpolation_meth }, // Interpolation fo `x2`
+    };
+
+    // Define the unphysical scale objects
+    pineappl_scale_func_form scale_mu = { PINEAPPL_SCALE_FUNC_FORM_SCALE, 0 };
+    pineappl_scale_func_form mu_scales[3] = { scale_mu, scale_mu, scale_mu };
+
+    // ---
+    // Create the grid using the previously set information about orders, bins and channels
+
+    auto* grid = pineappl_grid_new2(bins.size() - 1, bins.data(), orders.size() / 5, orders.data(),
+        channels, pid_basis, convs, 3, interpolations, kinematics, mu_scales);
+
+    pineappl_channels_delete(channels);
+
+    // ---
+    // Fill the grid with phase-space points
+    fill_grid(grid, kin_obs);
+
+    // ---
+    // NOTE: We now have to remap the bins to 3D
+
+    // We need to flatten the array of `KinematicsTuple` and define the normalizations
+    std::vector<double> flat_kin_obs;
+    for (const auto& kin : kin_obs) {
+        flat_kin_obs.push_back(std::get<0>(kin));
+        flat_kin_obs.push_back(std::get<1>(kin));
+        flat_kin_obs.push_back(std::get<2>(kin));
+    }
+    std::vector<double> normalizations(bins.size() - 1, 1.0);
+    pineappl_grid_set_bwfl(
+        grid,
+        flat_kin_obs.data(), // lower bin limits
+        flat_kin_obs.data(), // upper bin limits
+        bins.size() - 1, // number of bins
+        3, // Dimension of the bins (Q2, x, z)
+        normalizations.data()
+    );
+    pineappl_grid_optimize(grid);
+
+    // ---
+    // Write the grid to disk - the filename can be anything ...
+    std::string filename = "sidis-toygrid.pineappl.lz4";
+    pineappl_grid_write(grid, filename.c_str());
+
+    // destroy the object
+    pineappl_grid_delete(grid);
+
+    std::cout << "Generated " << filename << " containing a toy SIDIS.\n\n"
+        "Try running the following command to check the bins:\n"
+        "  - pineappl read --bins " << filename << "\n";
+}

examples/cpp/set-subgrids.output

@@ -0,0 +1,4 @@
+Generated sidis-toygrid.pineappl.lz4 containing a toy SIDIS.
+
+Try running the following command to check the bins:
+  - pineappl read --bins sidis-toygrid.pineappl.lz4

pineappl_capi/src/lib.rs

@@ -63,9 +63,10 @@ use pineappl::evolution::{AlphasTable, OperatorSliceInfo};
 use pineappl::fk_table::{FkAssumptions, FkTable};
 use pineappl::grid::{Grid, GridOptFlags};
 use pineappl::interpolation::{Interp as InterpMain, InterpMeth, Map, ReweightMeth};
-use pineappl::packed_array::ravel_multi_index;
+use pineappl::packed_array::PackedArray;
+use pineappl::packed_array::{ravel_multi_index, unravel_index};
 use pineappl::pids::PidBasis;
-use pineappl::subgrid::Subgrid;
+use pineappl::subgrid::{ImportSubgridV1, Subgrid};
 use std::collections::HashMap;
 use std::ffi::{CStr, CString};
 use std::fs::File;
@@ -2114,6 +2115,104 @@ pub unsafe extern "C" fn pineappl_grid_subgrid_array(
     }
 }
 
+/// Set the subgrid of a Grid for a given bin, order, and channel.
+///
+/// # Safety
+///
+/// If `grid` does not point to a valid `Grid` object, for example when `grid` is the null pointer,
+/// this function is not safe to call.
+#[no_mangle]
+pub unsafe extern "C" fn pineappl_grid_set_subgrid(
+    grid: *mut Grid,
+    bin: usize,
+    order: usize,
+    channel: usize,
+    node_values: *mut f64,
+    subgrid_array: *mut f64,
+    subgrid_shape: *mut usize,
+) {
+    let grid = unsafe { &mut *grid };
+    let num_kins = grid.kinematics().len();
+
+    let subgrid_shape = unsafe { slice::from_raw_parts(subgrid_shape, num_kins) };
+    let subgrid_array =
+        unsafe { slice::from_raw_parts(subgrid_array, subgrid_shape.iter().product()) };
+
+    let node_values: Vec<Vec<f64>> = {
+        let mut offset = 0;
+        subgrid_shape
+            .iter()
+            .map(|&dim_size| {
+                let dim_nodes =
+                    unsafe { slice::from_raw_parts(node_values.add(offset), dim_size) }.to_vec();
+                offset += dim_size;
+                dim_nodes
+            })
+            .collect()
+    };
+
+    let mut sparse_array: PackedArray<f64> =
+        PackedArray::new(node_values.iter().map(Vec::len).collect());
+
+    for (index, value) in subgrid_array
+        .iter()
+        .enumerate()
+        .filter(|(_, value)| **value != 0.0)
+    {
+        let index_unravel = unravel_index(index, subgrid_shape);
+        sparse_array[index_unravel.as_slice()] = *value;
+    }
+
+    let subgrid = ImportSubgridV1::new(sparse_array, node_values);
+    grid.subgrids_mut()[[order, bin, channel]] = subgrid.into();
+}
+
+/// Redefine the bin representation of the Grid; generalization of `pineappl_grid_set_remapper`.
+///
+/// # Panics
+///
+/// TODO
+///
+/// # Safety
+///
+/// If `grid` does not point to a valid `Grid` object, for example when `grid` is the null pointer,
+/// this function is not safe to call.
+#[no_mangle]
+pub unsafe extern "C" fn pineappl_grid_set_bwfl(
+    grid: *mut Grid,
+    bins_lower: *mut f64,
+    bins_upper: *mut f64,
+    n_bins: usize,
+    bin_dim: usize,
+    normalizations: *mut f64,
+) {
+    let grid = unsafe { &mut *grid };
+
+    let bins_lower = unsafe { slice::from_raw_parts(bins_lower, bin_dim * n_bins) };
+    let bins_upper = unsafe { slice::from_raw_parts(bins_upper, bin_dim * n_bins) };
+    let normalizations = unsafe { slice::from_raw_parts(normalizations, n_bins) };
+
+    let limits: Vec<Vec<(f64, f64)>> = bins_lower
+        .chunks(bin_dim)
+        .zip(bins_upper.chunks(bin_dim))
+        .map(|(bl_chunk, bu_chunk)| {
+            bl_chunk
+                .iter()
+                .zip(bu_chunk.iter())
+                .map(|(&a, &b)| (a, b))
+                .collect()
+        })
+        .collect();
+
+    grid.set_bwfl(
+        BinsWithFillLimits::from_limits_and_normalizations(limits, normalizations.to_vec())
+            // UNWRAP: error handling in the CAPI is to abort
+            .unwrap(),
+    )
+    // UNWRAP: error handling in the CAPI is to abort
+    .unwrap();
+}
+
 /// Get the shape of the objects represented in the evolve info.
 ///
 /// # Safety