add virtual dataset

docs/juliacon_2023/juliacon_2023_presentation.md

@@ -335,6 +335,28 @@ Where are the compressed chunks and can we decompress them in parallel?
 * Currently, HDF5.jl allows contiguous datasets to be memory mapped into arrays allowing for multithreaded reads.
 * With efficient chunk iteration, could we perform parallel decompression in HDF5.jl by reading compressed chunks directly?
 
+---
+# Virtual datasets
+
+- Maps multiple datasets into a single dataset
+ - Can be same or different files
+ - Supports patterns for sequentially numbered files/datasets
+
+- e.g. consider a dataset made up of 100×10 blocks, across 4 files
+ - `data00.h5`, `data01.h5`, etc.
+
+```julia
+space = dataspace((100,40))
+create_dataset(h5f, "dataset", datatype, space;
+ virtual=[HDF5.VirtualMapping(
+ HDF5.hyperslab(space, (1:100, HDF5.BlockRange(1:10; count = -1))), # block pattern
+ "./data0%b.h5", # filenames (%b block pattern)
+ "data", # path to source dataset in file
+ dataspace((100,10)) # view into source dataset
+ )]
+)
+```
+
 ---
 
 # Parallelization via MPI