lowdisc — Low Discrepancy Sequences for Scilab

Low-discrepancy (quasi-random) sequence generators for Scilab: Halton (classic, leaped, reverse, scrambled), Sobol (classic and scrambled), Faure, and Niederreiter (arbitrary base). These sequences give a higher convergence rate than pseudo-random numbers in Monte-Carlo simulation and numerical integration, for problems of arbitrary dimension.

Features:

• arbitrary number of dimensions;
• skip a given number of initial elements; leap (ignore) elements between draws;
• fast sequences backed by compiled C/C++;
• helpers that suggest optimal settings per sequence;
• object-oriented API (lowdisc_new / lowdisc_get / lowdisc_next / lowdisc_destroy) plus the one-shot lowdisc_ldgen(callf, n, ldseq);
• direct access to the k-th coordinate without generating coordinates 1..k-1.

Modernized for Scilab 2026.1.0

This is the lowdisc 0.7 toolbox (Michael Baudin — INRIA / DIGITEO, 2008–2014), ported to build and run on Scilab 2026.1.0. The original C++ gateways were written against the Scilab 5 stack-c.h API, which Scilab 6 removed; they have been rewritten against the modern api_scilab interface.

What changed:

• All 28 C++ gateways migrated from stack-c.h to api_scilab; gateway signatures int sci_xxx(char *fname) → int sci_xxx(char *fname, void *pvApiCtx).
• Scilab 6 dropped the implicit global pvApiCtx that the support helpers relied on; each gateway now sets a translation-unit global from its pvApiCtx argument before calling any helper (the helpers keep their original signatures).
• Reworked the gateway support layer: the dead GetRhsVarMatrixDouble macro was replaced by a new lowdisc_GetMatrixOfDoubleArgument helper (getVarAddressFromPosition + getMatrixOfDouble); single-string arguments now use getAllocatedSingleString; variable-type checks use getVarType.
• tbx_builder_help wrapped in try/catch so a headless (CLI) build completes even when the help chapter can't be built.
• The pure-numeric C++ library under src/cpp was unchanged — it uses no Scilab API.

The numerical results were verified end-to-end on Scilab 2026.1.0: all seven sequence types produce points in [0,1]^n of the expected shape via lowdisc_ldgen.

Dependencies

Requires two ATOMS toolboxes (both pure-macro), loaded automatically by Scilab before lowdisc:

• apifun — argument-checking helpers;
• number — prime-number tables (number_primes100, …) used for Halton/Faure bases.

Building

exec builder.sce;   // compiles src/cpp + the 28 gateways, builds macros, generates loader.sce
exec loader.sce;    // loads the toolbox into the running session

License

GNU LGPL — see license.txt. The interface and numerical sources are distributed under the LGPL / CeCILL terms noted in the individual file headers.

Credits

Original toolbox by Michael Baudin (INRIA, DIGITEO / Scilab Enterprises), 2008–2014. Scilab 2026 modernization preserves the original algorithms and public API.