diff options
Diffstat (limited to 'doc/examples')
| -rw-r--r-- | doc/examples/04_compress_easy_mt.c | 30 |
1 files changed, 26 insertions, 4 deletions
diff --git a/doc/examples/04_compress_easy_mt.c b/doc/examples/04_compress_easy_mt.c index 121d3b11..efe56975 100644 --- a/doc/examples/04_compress_easy_mt.c +++ b/doc/examples/04_compress_easy_mt.c @@ -31,10 +31,6 @@ init_encoder(lzma_stream *strm) // No flags are needed. .flags = 0, - // Set the number of threads to use. - // FIXME: Add how to autodetect a reasonable number. - .threads = 4, - // Let liblzma determine a sane block size. .block_size = 0, @@ -57,6 +53,32 @@ init_encoder(lzma_stream *strm) .check = LZMA_CHECK_CRC64, }; + // Detect how many threads the CPU supports. + mt.threads = lzma_cputhreads(); + + // If the number of CPU cores/threads cannot be detected, + // use one thread. Note that this isn't the same as the normal + // single-threaded mode as this will still split the data into + // blocks and use more RAM than the normal single-threaded mode. + // You may want to consider using lzma_easy_encoder() or + // lzma_stream_encoder() instead of lzma_stream_encoder_mt() if + // lzma_cputhreads() returns 0 or 1. + if (mt.threads == 0) + mt.threads = 1; + + // If the number of CPU cores/threads exceeds threads_max, + // limit the number of threads to keep memory usage lower. + // The number 8 is arbitrarily chosen and may be too low or + // high depending on the compression preset and the computer + // being used. + // + // FIXME: A better way could be to check the amount of RAM + // (or available RAM) and use lzma_stream_encoder_mt_memusage() + // to determine if the number of threads should be reduced. + const uint32_t threads_max = 8; + if (mt.threads > threads_max) + mt.threads = threads_max; + // Initialize the threaded encoder. lzma_ret ret = lzma_stream_encoder_mt(strm, &mt); |