<?php $idpost=0; ?>
<?php global $paged;
if ( get_query_var('paged') ) {
    $paged = get_query_var('paged');
} else if ( get_query_var('page') ) {
    $paged = get_query_var('page');
} else {
    $paged = 1;
}
$args = array( 'post_type' => 'post', 'paged' => $paged );

$q = new WP_Query( $args );
            ?>
<?php if ($q->have_posts()) : ?>
<?php while($q->have_posts()) : $q->the_post(); ?>

<?php if  (!is_paged()) { ?>
    <li class="thum_<?php echo $idpost; ?>"><a href="<?php the_permalink() ?>"><?php the_post_thumbnail(); ?></a><br />
    <a class="sname" href="<?php the_permalink() ?>"><?php the_title(); ?></a>
    </li>
<?php } else { ?>
    <li class="thums_<?php echo $idpost; ?>"><a href="<?php the_permalink() ?>"><?php the_post_thumbnail(); ?></a><br />
    <a class="sname" href="<?php the_permalink() ?>"><?php the_title(); ?></a>
    </li>
<?php } $idpost++; endwhile; ?>
    </ul>
    <div style="clear:both"></div>
        <?php  if ( function_exists('wp_pagenavi') ) { ?>
            <div id="wp-pagenavibox"><?php wp_pagenavi( array('query' => $q) ); ?></div>
        <?php } endif; ?>
<?php wp_reset_postdata(); ?>


// in functions I am using
function custom_posts_per_page($query) {
if (is_home() && !is_paged()) {
  $query->query_vars['posts_per_page'] = 8;
  return $query;
  } else {
  $query->query_vars['offset'] = 8;
  return $query;
  }
}
add_filter('pre_get_posts', 'custom_posts_per_page');