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