How-to build: emscripten + gsl

blas-sample.c

#include <stdio.h>
#include <gsl/gsl_blas.h>

int
main (void)
{
  double a[] = { 0.11, 0.12, 0.13,
                 0.21, 0.22, 0.23 };

  double b[] = { 1011, 1012,
                 1021, 1022,
                 1031, 1032 };

  double c[] = { 0.00, 0.00,
                 0.00, 0.00 };

  gsl_matrix_view A = gsl_matrix_view_array(a, 2, 3);
  gsl_matrix_view B = gsl_matrix_view_array(b, 3, 2);
  gsl_matrix_view C = gsl_matrix_view_array(c, 2, 2);

  /* Compute C = A B */

  gsl_blas_dgemm (CblasNoTrans, CblasNoTrans,
                  1.0, &A.matrix, &B.matrix,
                  0.0, &C.matrix);

  printf ("[ %g, %g\n", c[0], c[1]);
  printf ("  %g, %g ]\n", c[2], c[3]);

  return 0;
}

build-gsl-emscripten.sh

#!/bin/bash

# This gisted shell script presents linking details when converting C programs into wasm
# through kripken's emscripten. In this language convertion, emcc is the tool that will
# replace gcc. emconfigure and emmake will replace ./configure and make. It is straight
# forward for C language advanced programmers, but it may not # be the case for HTML+CSS+
# Javascript developers.
#
# The prior readings:
#   - https://developers.google.com/web/updates/2018/03/emscripting-a-c-library
#   - https://kripken.github.io/emscripten-site/docs/compiling/Building-Projects.html

# Dependencies:
#   -git, wget,tar
#   -nodejs

INITIAL_DIR=$(pwd)

GSL_LATEST_URL="ftp://ftp.gnu.org/gnu/gsl/gsl-latest.tar.gz"
GSL_LATEST_FILE="gsl-latest.tar.gz"

EMSDK_GIT_URL="https://github.com/juj/emsdk.git"

# Download emscripten
git clone "$EMSDK_GIT_URL"
cd emsdk
git pull
./emsdk install latest
./emsdk activate latest
EMMAKE_RUNNABLE=$(find $(pwd) -name 'emmake'      | head -n 1)
EMCONF_RUNNABLE=$(find $(pwd) -name 'emconfigure' | head -n 1)
EMCC___RUNNABLE=$(find $(pwd) -name 'emcc'        | head -n 1)

# Download gsl
cd "$INITIAL_DIR"
wget "$GSL_LATEST_URL" --output-document "$GSL_LATEST_FILE"
tar xf "$GSL_LATEST_FILE"
cd $(find . -maxdepth 1 -type d | grep gsl)
$EMCONF_RUNNABLE ./configure
$EMMAKE_RUNNABLE make

# Compiles any 'main.c' program that depends on gsl like this:
#
#     $ emcc main.c .libs/libgsl.so.23 cblas/*.o -I . -lm
#
# '.libs/libgsl.so.23'
#     path to the gsl llvm compiled library
# 'cblas/*.o'
#     pattern that refers to the remaining compiled objs
# '-I .'
#     CFLAGS to include necessary headers from main.c
# '-lm'
#     CFLAGS to include math.h
#
# PS: it also works fine with gcc like this:
#
#     $ gcc main.c .libs/libgsl.so.23 cblas/*.o -I . -lm
#

# Runnning llvm-nm on libgsl.so.23 should reveal cblas_x 
# objects are just referenced but undefined by the library
#
#     $ llvm-nm .libs/libgsl.so.23
# (...)
#     u atanh
#     U calloc
#     U cblas_caxpy         # <- NOTE THOSE
#     U cblas_ccopy         #     ... and later ones
# (...)

LIBGSLSO_PATH=$(find . -name 'libgsl.so.23' )
CBLAS_BC_PATH=$(find . -name 'CBLAS' -type d)

cp "$INITIAL_DIR/blas-sample.c" .     # NOTE: have the c files on the initial directory
cp "$INITIAL_DIR/mult-sample.c" .     #     otherwise move it manualy

gcc "$LIBGSLSO_PATH" "$CBLAS_BC_PATH/*.o" blas-sample.c -I . -lm -o blas-sample.js
gcc "$LIBGSLSO_PATH" "$CBLAS_BC_PATH/*.o" mult-sample.c -I . -lm -o mult-sample.js

node.js blas-sample.js
node.js mult-sample.js

# Check if the output from node is as expected

# Loading the js and wasm on Chrome should also be working fine:
#   - move the blas-sample.js and blas-sample.wasm to the apache dir
#   - on the html load blas-sample.js file with <script src='path'> tag
#   - output should be printed on the console ('ctrl+shift+i')

mult-sample.c

#include <gsl/gsl_multimin.h>

/* Paraboloid centered on (p[0],p[1]), with
   scale factors (p[2],p[3]) and minimum p[4] */

double my_f (const gsl_vector *v, void *params)
{
  double x, y;
  double *p = (double *)params;

  x = gsl_vector_get(v, 0);
  y = gsl_vector_get(v, 1);

  return p[2] * (x - p[0]) * (x - p[0]) +
           p[3] * (y - p[1]) * (y - p[1]) + p[4];
}



/* The gradient of f, df = (df/dx, df/dy). */
void my_df (const gsl_vector *v, void *params,
       gsl_vector *df)
{
  double x, y;
  double *p = (double *)params;

  x = gsl_vector_get(v, 0);
  y = gsl_vector_get(v, 1);

  gsl_vector_set(df, 0, 2.0 * p[2] * (x - p[0]));
  gsl_vector_set(df, 1, 2.0 * p[3] * (y - p[1]));
}



/* Compute both f and df together. */
void my_fdf (const gsl_vector *x, void *params,
        double *f, gsl_vector *df)
{
  *f = my_f(x, params);
  my_df(x, params, df);
}



int main (void) {
  size_t iter = 0;
  int status;

  const gsl_multimin_fdfminimizer_type *T;
  gsl_multimin_fdfminimizer *s;

  /* Position of the minimum (1,2), scale factors
     10,20, height 30. */
  double par[5] = { 1.0, 2.0, 10.0, 20.0, 30.0 };

  gsl_vector *x;
  gsl_multimin_function_fdf my_func;

  my_func.n = 2;
  my_func.f = my_f;
  my_func.df = my_df;
  my_func.fdf = my_fdf;
  my_func.params = par;

  /* Starting point, x = (5,7) */
  x = gsl_vector_alloc (2);
  gsl_vector_set (x, 0, 35.0);
  gsl_vector_set (x, 1, 27.0);

  T = gsl_multimin_fdfminimizer_conjugate_fr;
  s = gsl_multimin_fdfminimizer_alloc (T, 2);

  gsl_multimin_fdfminimizer_set (s, &my_func, x, 0.01, 1e-14);

  do
    {
      iter++;
      status = gsl_multimin_fdfminimizer_iterate (s);

      if (status)
         break;

      status = gsl_multimin_test_gradient (s->gradient, 1e-3);

      if (status == GSL_SUCCESS) 
         printf ("Minimum found at:\n");

      printf ("%5d %.5f %.5f %10.5f\n", iter,
              gsl_vector_get (s->x, 0),
              gsl_vector_get (s->x, 1),
              s->f);

    }
  while (status == GSL_CONTINUE && iter < 100);

  gsl_multimin_fdfminimizer_free (s);
  gsl_vector_free (x);

  return 0;
}