/**
@page working_with_memory Working with Memory and Performance

@tableofcontents

@section ww_mem_constant Constant Memory Mode

By default libxlsxwriter holds all cell data in memory. This is to allow
non-sequential data storage and also to allow future features where formatting
is applied separately from the data.

The effect of this is that for large files libxlsxwriter can consume a lot of
memory.

Fortunately, this memory usage can be reduced almost completely by using
workbook_new_opt() and the lxw_workbook_options `constant_memory` property:

@dontinclude constant_memory.c
@skipline include
@until    return
@skipline }

This optimization works by flushing each row after a subsequent row is written.
In this way the largest amount of data held in memory for a worksheet is the
amount of data required to hold a single row of data.

If required, this memory usage can be reduced even more by setting
`LXW_COL_MAX` in worksheet.c from 16384 down to a value that matches the
maximum column that is likely to be encountered.

The trade-off when using `constant_memory` mode is that data must be added
sequentially in row order and you won't be able to take advantage of any
functions that manipulate cell data after it is written. One such feature is
worksheet_set_row() which in `constant_memory` mode can only be used when
writing data to the current row. Another is worksheet_merge_range() which can
only be applied to a merged range in the current row.

@section ww_mem_row_order Row Column Order

Since each new row flushes the previous row, data must be written in sequential
row order when `constant_memory` mode is on:

@code
    lxw_workbook  *workbook  = workbook_new_opt("constant_memory.xlsx", &options);
    ...

    // !! Don't use "column x row" order in 'constant_memory' mode. Only
    //    the first column of data will be written.
    for (col = 0; col < max_col; col++) {
        for (row = 0; row < max_row; row++) {
            worksheet_write_number(worksheet, row, col, 123.45, NULL);
        }
   -*- mode:  }
 @endcode

@section ww_mem_inline_strings Inline strings

Another optimization that is used to reduce memory usage in `constant_memory`
mode is that cell strings aren't stored in an Excel structure call "shared
strings" and instead are written "in-line". This is a documented Excel feature
that is supported by most spreadsheet applications. One known exception is
Apple Numbers for Mac where the string data isn't displayed.

@section ww_mem_performance Performance

Currently the library isn't highly optimized. Also, the library is currently
single threaded.


Next: @ref working_with_macros


*/