GRIB Import

Tensogram provides tensogram-grib, a dedicated crate for importing GRIB (GRIdded Binary) messages into Tensogram format. GRIB is widely used in operational weather forecasting; this importer lets you bring existing GRIB data into Tensogram pipelines while preserving the full MARS namespace metadata. Conversion is one-way: GRIB → Tensogram.

System Requirement

The ecCodes C library must be installed:

brew install eccodes       # macOS
apt install libeccodes-dev # Debian/Ubuntu

Building

The tensogram-grib crate is excluded from the default workspace build to avoid requiring ecCodes on machines that do not need GRIB import.

# Build the library
cd rust/tensogram-grib && cargo build

# Build CLI with GRIB support
cargo build -p tensogram-cli --features grib

Conversion Modes

Merge All (default)

All GRIB messages are combined into a single Tensogram message with N data objects. ALL MARS keys for each GRIB message are placed into the corresponding base[i] entry independently — there is no common/varying partitioning in the output.

tensogram convert-grib forecast.grib -o forecast.tgm

One-to-One (split)

Each GRIB message becomes a separate Tensogram message with one data object. All MARS keys go into base[0].

tensogram convert-grib forecast.grib -o forecast.tgm --split

Rust API

#![allow(unused)]
fn main() {
use std::path::Path;
use tensogram_grib::{convert_grib_file, ConvertOptions, Grouping};

let options = ConvertOptions {
    grouping: Grouping::MergeAll,
    ..Default::default()
};

let messages = convert_grib_file(Path::new("forecast.grib"), &options)?;
// messages is Vec<Vec<u8>> — each element is a complete Tensogram wire-format message
}

Data Mapping

Source (GRIB)	Target (Tensogram)
Grid values (`values` key)	Data object payload (float64, little-endian)
Grid dimensions (Ni, Nj)	`DataObjectDescriptor.shape` as `[Nj, Ni]`
Reduced Gaussian grids (Ni=0)	Shape `[numberOfPoints]` (1D)
MARS keys (all, per message)	`GlobalMetadata.base[i]["mars"]` (each entry independent)

Scope

Only GRIB → Tensogram import is supported. Tensogram → GRIB is out of scope because Tensogram’s N-tensor data model is a superset of GRIB’s 2-D-field model; a faithful down-conversion is often impossible.

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