// There are more entries. Read an extension header and parse its entries.
			if _, err := mustReadFull(tr.r, blk[:]); err != nil {
				return nil, err
			}
			s = blk.toSparse()
			continue
		}
		return spd, nil // Done
	}
}

// readGNUSparseMap1x0 reads the sparse map as stored in GNU's PAX sparse format
// version 1.0. The format of the sparse map consists of a series of

	// Keywords for GNU sparse files in a PAX extended header.
	paxGNUSparse          = "GNU.sparse."
	paxGNUSparseNumBlocks = "GNU.sparse.numblocks"
	paxGNUSparseOffset    = "GNU.sparse.offset"
	paxGNUSparseNumBytes  = "GNU.sparse.numbytes"
	paxGNUSparseMap       = "GNU.sparse.map"
	paxGNUSparseName      = "GNU.sparse.name"
	paxGNUSparseMajor     = "GNU.sparse.major"
	paxGNUSparseMinor     = "GNU.sparse.minor"

			}, nil},
			testClose{nil},
		},
		// TODO(dsnet): Re-enable this test when adding sparse support.
		// See https://golang.org/issue/22735
		/*
			}, {
				file: "testdata/gnu-nil-sparse-data.tar",
				tests: []testFnc{
					testHeader{Header{
						Typeflag:    TypeGNUSparse,
						Name:        "sparse.db",
						Size:        1000,
						SparseHoles: []sparseEntry{{Offset: 1000, Length: 0}},

  private static final ImmutableSet<Character> ROW_SPACE = ImmutableSet.of('a', 'b');

  private static final ImmutableSet<Integer> COLUMN_SPACE = ImmutableSet.of(1, 2);

  private static final SparseImmutableTable<Character, Integer, String> SPARSE =
      new SparseImmutableTable<>(CELLS.asList(), ROW_SPACE, COLUMN_SPACE);

  private static final DenseImmutableTable<Character, Integer, String> DENSE =

  private static final ImmutableSet<Character> ROW_SPACE = ImmutableSet.of('a', 'b');

  private static final ImmutableSet<Integer> COLUMN_SPACE = ImmutableSet.of(1, 2);

  private static final SparseImmutableTable<Character, Integer, String> SPARSE =
      new SparseImmutableTable<>(CELLS.asList(), ROW_SPACE, COLUMN_SPACE);

  private static final DenseImmutableTable<Character, Integer, String> DENSE =

import com.google.errorprone.annotations.Immutable;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;

/** A {@code RegularImmutableTable} optimized for sparse data. */
@GwtCompatible
@Immutable(containerOf = {"R", "C", "V"})
@ElementTypesAreNonnullByDefault
final class SparseImmutableTable<R, C, V> extends RegularImmutableTable<R, C, V> {

    assertThat(copy.values()).containsExactly("baz", "bar", "foo").inOrder();
    assertThat(copy.row('b').keySet()).containsExactly(1, 2).inOrder();
  }

  public void testBuilder_orderRowsAndColumnsBy_sparse() {
    ImmutableTable.Builder<Character, Integer, String> builder = ImmutableTable.builder();
    builder.orderRowsBy(Ordering.natural());
    builder.orderColumnsBy(Ordering.natural());
    builder.put('x', 2, "foo");

    assertThat(copy.values()).containsExactly("baz", "bar", "foo").inOrder();
    assertThat(copy.row('b').keySet()).containsExactly(1, 2).inOrder();
  }

  public void testBuilder_orderRowsAndColumnsBy_sparse() {
    ImmutableTable.Builder<Character, Integer, String> builder = ImmutableTable.builder();
    builder.orderRowsBy(Ordering.natural());
    builder.orderColumnsBy(Ordering.natural());
    builder.put('x', 2, "foo");

*   `tf.sparse.segment_sum` `tf.sparse.segment_mean` `tf.sparse.segment_sqrt_n` `SparseSegmentSum/Mean/SqrtN[WithNumSegments]`

    *   Added `sparse_gradient` option (default=false) that makes the gradient of these functions/ops sparse (`IndexedSlices`) instead of dense (`Tensor`), using new `SparseSegmentSum/Mean/SqrtNGradV2` ops.

*   `tf.nn.embedding_lookup_sparse`

      .isEqualTo("<< 0x00000003 10000 DATA          COMPRESSED")
  }

  /**
   * Ensures that valid flag combinations appear visually correct, and invalid show in hex.  This
   * also demonstrates how sparse the lookup table is.
   */
  @Test
  fun allFormattedFlagsWithValidBits() {
    val formattedFlags = mutableListOf<String>() // Highest valid flag is 0x20.