Build 4.0.0.51 of xlsgen makes an important performance gain for processing large spreadsheets.

Those Excel files can be either legacy (XLS, ...) or modern (XLSX, ...). The class of large spreadsheets being adressed by this build is one made of many rows with columns not on the left of the spreadsheet. For instance, if many columns filled with data/formulas begin at 800 (or ADT in terms of column reference), previous builds of xlsgen would pre-allocate 800 columns in memory for this row alone. With this build, only column 800 and a few more are pre-allocated. This, as is obvious, has an important consequence for the memory consumption for loading, processing and writing the files. And you can expect up to 90% less memory consumption in such scenario. Many scenarios that would have required a 64-bit version of xlsgen would simply work fine on the regular 32-bit version of xlsgen (the 32-bit version of xlsgen can hold only 2GB of working memory due to the 32-bit per running process Windows restrictions).