parse_ctrees

Header-only C code to robustly parse output from Consistent-Trees (mergertree code for cosmological simulations)

Why this code exists

I have frequently needed to parse Consistent-Trees files in C and always have to count up the column numbers by hand (for each simulation) and make sure I am reading the correct columns (in my ConvertCtrees code). Multiple times I have messed up the counting and produced incorrect results downstream, requiring another conversion process.

I am planning to solve this issue once and for all.

What the Code can do

The code reads a single tree at a time. For each tree, the code can efficiently do the following:

• Automatically parse the header and then read all/some of the columns present in Consistent Trees output
• Assign each column to multiple memory locations
• Handle assignments to both structure-of-arrays and array-of-structures
• Account for changes in column-naming convention in Consistent Trees (e.g., snap_num vs snap_idx)
• Perform various error-checking to "Not Do the Wrong Thing"™

Code Design

In the general case, any column from the Consistent-Trees output (i.e., something like tree_?_?_?.dat) can be assigned to an arbitrary pointer. Every requested column has a column number, column type, a destination base pointer, size of each element of the destination base pointer, and an offset in bytes to reach the field (only relevant for compound types like struct or unions).

Example Usage

See in action here

Prior Work

Yao-Yuan Mao has an excellent python reader for Consistent-Trees here