cpp_int initialization inefficient

[Manfred Weis <manfredweis@…>]

I tried to create an cpp_int with about 10 million digits from a hex string "0x1....1"; it literally take ages. The reasons seems to be the repeated shift and add conversion from the characters; while that is inevitable for decimal digits, a hex encoded string would allow to directly determine the final position and shift in the corresponding limb.

TODO: check supplied string for valid hex encoding, allocate enough zero-initialized limbs and then directly set the value of the corresponding limb.

A further improvement would be to supply a conversion from a sequence of values that are stored in some linear container.

[anonymous]

Will fix shortly.

[John Maddock]

I believe this is now fixed in develop for hex and octal numbers.

Docs for import/export to external storage here: ​https://rawgit.com/boostorg/multiprecision/develop/doc/html/boost_multiprecision/tut/import_export.html, comments welcome.