template-grid-archive.php

<?php
/* Template Name: Grid Archive */

/**
 * Grid Archive Loop
 * 
 */
function be_grid_archive_loop() {
  $categories = get_categories();
  foreach( $categories as $category ) {
    
    $args = array(
      'posts_per_page' => -1,
      'post_type' => 'post',
      'cat' => $category->term_id,
    );
    $loop = new WP_Query( $args );
    
    if( $loop->have_posts() ) {
      echo '<h3>' . $category->name . '</h3>';
      echo '<div class="grid-listing">';
      
      while( $loop->have_posts() ) { 
        $loop->the_post();
        global $post;
        
        $class = 0 == $loop->current_post || 0 == $loop->current_post % 2 ? 'one-half first' : 'one-half';
        echo '<div class="' . $class . '">';
        echo '<p class="title"><a href="' . get_permalink() . '">' . get_the_title() . '</a></p>';
        echo '<p class="image"><a href="' . get_permalink() . '">' . get_the_post_thumbnail( $post->ID, 'grid-thumbnail' ) . '</a></p>';
        echo '</div>';
        
      } // endwhile  
      
      echo '</div>';
    } // endif
    
  } // endforeach
  wp_reset_postdata();
}
add_action( 'genesis_loop', 'be_grid_archive_loop' );
remove_action( 'genesis_loop', 'genesis_do_loop' );

genesis();