The BookStore is an Object which managed Histograms for later universal access.

See dependency diagram for further information.

Entry Types

Depending on the use case, the BookStore can provide your object in different ways.

• Single

  For usage in sequential code, minimal management overhead.

• Multi
  usage for may modifying the object in parallel.

  • MultiCopy instantiate object mutable times to avoid synchronisation. Memory overhead.
    The number of instances must be passed to construct time.

    use case: high frequent writing operation.

  • MultiShared creates object accessible with writer, to keep object valid locks are used. Many synchronisation points.

    use case: much computing and only low frequent writing.

Creating new objects

1. Construct EntryData (blueprint) for the object to book
2. Book object with book(absolute-path, name, entry-data)

examples

• for a single Hist1F

    EntryData entry-data = EntryData<Hist1F>("title", {"axis title", bins, min, max});
    auto entry = store.book("/path/to/object/", "name", entry-data.single());

• for a multi copy, with 4 instances, Hist1F

    auto entry = store.book("/path/", "name", EntryData<Hist1F>(axis).multiCopy(4));

• for a single Hist2F

    auto entry = store.book("/path/", "name", EntryData<Hist2F>(axis1, axis2).single());

Writing to an object

creating a handle

entry.handle() will produce a new handle.
For EntryMultiCopy you need to pass the id of the instance you want to access entry.handle(id).

example Hist1F

    // single
    Handle<Hist1F> entrySingle.handle();

    // multi copy
    Handle<Hist1F> entryMultiCopy.handle(0);

    //multi shared
    Handle<Hist1F> entryMultiShared.handle();

use the object specific modification functions.

• Histogram
  • fill(position, weight)
    add one datum to the histogram, position array based type which fields equal to the number of dimensions from the histogram.
    e.g 1D fill({x}, w), 2D fill({x,y},w), etc.
  • fillN(containerType positions, containerType weights)
    add mutable dates to the histogram.

example Hist1F

    handle.fill({1}, 1);

    std::vector<typename Hist1F::Point_t> points = {…};
    std::vector<typename Hist1F::Weight_t> weights = {…};
    handle.fillN(points, weights);

reading final version of object

entry.merged() returns a const reference to the final object.

example Hist1F

    const Hist1F& hist = entry.merged();
    // now you can read the histogram normally
    std::cout << hist.GetBinContent({0}) << '\n';

Access created objects

selection

Set of entries which full fill a condition. Can created from a BookStore or an other Selection.

features * iterate able
* manually removing from elements * access entries

Condition

A Condition for filtering entries. Constructed with ConditionBuilder.

attributes to filter

• name: perfect match or regex
• path: perfect match or regex
• type: perfect match

example

    Condition condition = ConditionBuilder()
        .setName("name") // perfect match to name required
        .setPath(std::regex("^p[^/]*h")); // path must match regex

example get a handle from every Hist1F in /path/to/dir

    Selection selection = store.find(
        ConditionBuilder().setPath("/path/to/dir/")
    );

    try {
        for(const entry& : selection) {
            handles<Hist1F>.push_back(entry.handle<Hist1F>());
        }
    } catch (const marlin::BookStoreException&){}