start half-float experiment
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John Cupitt
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0b3d7fc185
@ -108,8 +108,8 @@
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/*
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#define DEBUG
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#define DEBUG_PIXELS
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#define DEBUG_COMPILE
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*/
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#define DEBUG_COMPILE
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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@ -161,9 +161,11 @@ typedef struct {
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int *coeff; /* Array of non-zero mask coefficients */
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int *coeff_pos; /* Index of each nnz element in mask->coeff */
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/* And a fixed-point version for a vector path.
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/* And a half float version for a vector path.
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*/
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int *fixed;
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int *mant;
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int exp;
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int n_point; /* Number of points in fixed-point array */
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/* The set of passes we need for this mask.
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@ -835,27 +837,28 @@ vips__image_intize( VipsImage *in, VipsImage **out )
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return( 0 );
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}
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/* Make an int version of a mask.
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*
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* This makes a fixed-point version ready for the vector path: instead of an
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* output scale, we have x.y for each element.
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/* Make an int version of a mask. Each element is 8.8 float, with the same
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* exponent for each element (so just 8 bits in @out).
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*
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* @out is a w x h int array.
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*/
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static int
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intize_to_fixed_point( VipsImage *in, int *out )
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intize_to_half_float( VipsImage *in, int *out, int *exp )
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{
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VipsImage *t;
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double scale;
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int ne;
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double *scaled;
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double mx;
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double above;
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int shift;
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double total_error;
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int i;
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if( vips_check_matrix( "vips2imask", in, &t ) )
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return( -1 );
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/* Bake the scale into the mask.
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/* Bake the scale into the mask to make a double version.
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*/
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scale = vips_image_get_scale( t );
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ne = t->Xsize * t->Ysize;
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@ -867,42 +870,54 @@ intize_to_fixed_point( VipsImage *in, int *out )
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scaled[i] = VIPS_MATRIX( t, 0, 0 )[i] / scale;
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g_object_unref( t );
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/* The scaled mask must fit in 3.5 bits, so we can handle -4 to +3.99
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*/
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for( i = 0; i < ne; i++ )
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if( scaled[i] >= 4.0 ||
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scaled[i] < -4 ) {
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g_info( "intize_to_fixed_point: "
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"out of range for vector path" );
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return( -1 );
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}
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#ifdef DEBUG_COMPILE
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{
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int x, y;
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/* The smallest coefficient we can manage is 1/32nd, we'll just turn
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* that into zero.
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*
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* Find the total error we'll get by rounding down to zero and bail if
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* it's significant.
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*/
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total_error = 0.0;
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for( i = 0; i < ne; i++ )
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if( scaled[i] != 0.0 &&
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VIPS_FABS( scaled[i] ) < 1.0 / FIXED_SCALE )
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total_error += VIPS_FABS( scaled[i] );
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/* 0.1 is a 10% error.
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*/
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if( total_error > 0.1 ) {
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g_info( "intize_to_fixed_point: too many underflows" );
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return( -1 );
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printf( "intize_to_half_float: double version\n" );
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for( y = 0; y < t->Ysize; y++ ) {
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printf( "\t" );
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for( x = 0; x < t->Xsize; x++ )
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printf( "%g ", scaled[y * t->Xsize + x] );
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printf( "\n" );
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}
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}
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#endif /*DEBUG_COMPILE*/
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vips_vector_to_fixed_point( scaled, out, ne, FIXED_SCALE );
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/* The mask max rounded up to the next power of two gives the exponent
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* all elements share.
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*/
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mx = scaled[0];
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for( i = 1; i < ne; i++ )
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if( scaled[i] > mx )
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mx = scaled[i];
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/* So eg. -3 for 1/8, 3 for 8.
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*/
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shift = ceil( log2( mx ) );
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/* Mask elements are schar. We convolve as:
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* 1. 8s*8u->16s
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* 2. shift down to make sure we have enough bits to sum all
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* elements --- ceil(log2(ne))
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* 3. 16s+16s->16s
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* 4. shift again by exp and take the top 8 bits
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* 5. clip to 0 - 255
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*/
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if( shift
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/* We do the exp by shifting after the mask sum
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*/
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*exp = above;
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for( i = 0; i < ne; i++ )
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out[i] = 256 * scaled[i] / above;
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#ifdef DEBUG_COMPILE
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{
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int x, y;
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printf( "intize_to_fixed_point:\n" );
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printf( "intize_to_half_float: exp = %d\n", *exp );
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for( y = 0; y < t->Ysize; y++ ) {
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printf( "\t" );
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for( x = 0; x < t->Xsize; x++ )
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@ -912,6 +927,25 @@ intize_to_fixed_point( VipsImage *in, int *out )
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}
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#endif /*DEBUG_COMPILE*/
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/* Convolve with 255 and calculate the total error.
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*/
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total_error = 0.0;
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for( i = 0; i < ne; i++ ) {
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double true_value = 255 * scaled[i];
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double approx_value = 255 * out[i] / (256 * above);
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double error = VIPS_FABS( true_value - approx_value );
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total_error += error;
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}
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/* 0.1 is a 10% error.
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*/
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if( total_error > 0.1 ) {
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g_info( "intize_to_half_float: too many underflows - "
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"%d%%i error", (int) (100 * total_error) );
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return( -1 );
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}
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return( 0 );
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}
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@ -952,8 +986,8 @@ vips_convi_build( VipsObject *object )
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*/
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if( vips_vector_isenabled() &&
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in->BandFmt == VIPS_FORMAT_UCHAR ) {
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if( (convi->fixed = VIPS_ARRAY( object, n_point, int )) &&
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!intize_to_fixed_point( M, convi->fixed ) &&
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if( (convi->mant = VIPS_ARRAY( object, n_point, int )) &&
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!intize_to_half_float( M, convi->mant, &convi->exp ) &&
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!vips_convi_compile( convi, in ) ) {
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generate = vips_convi_gen_vector;
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g_info( "convi: using vector path" );
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