Speed enhancement: alpha packing.

When the alpha channel is used in a color palette, the code now replaces
the blue channel in the accumulation buffer with a pair of two U16s,
which encode the values of the blue and alpha channels as a fraction of
the value of the density. When the alpha channel is always 1.0, the blue
channel works as normal. Density is now always the last element in the
accumulation buffer.

Eliminating the separate IO operations improved total runtime by more
than 30% on my card, while the extra calculations reduced that to 20%
when alpha was present (though that can be optimized further).
This commit is contained in:
Steven Robertson 2011-10-11 09:57:37 -04:00
parent a052f7f4c5
commit 618b51b1b1
4 changed files with 75 additions and 19 deletions

View File

@ -15,7 +15,7 @@ void colorclip(float4 *pixbuf, float gamma, float vibrancy, float highpow,
float4 pix = pixbuf[i];
if (pix.w <= 0) {
pixbuf[i] = make_float4(bkgd.x, bkgd.y, bkgd.z, 0);
pixbuf[i] = make_float4(bkgd.x, bkgd.y, bkgd.z, 0.0f);
return;
}
@ -121,7 +121,9 @@ __device__ void de_add(int ibase, int ii, int jj, float4 scaled) {
__global__
void logscale(float4 *pixbuf, float4 *outbuf, float k1, float k2) {
int i = blockDim.x * blockIdx.x + threadIdx.x;
float den;
float4 pix = pixbuf[i];
read_pix(pix, den);
float ls = fmaxf(0, k1 * logf(1.0f + pix.w * k2) / pix.w);
pix.x *= ls;
@ -138,7 +140,7 @@ void logscale(float4 *pixbuf, float4 *outbuf, float k1, float k2) {
#define MAX_SD 4.33333333f
__global__
void density_est(float4 *pixbuf, float4 *outbuf, float *denbuf,
void density_est(float4 *pixbuf, float4 *outbuf,
float est_sd, float neg_est_curve, float est_min,
float k1, float k2) {
for (int i = threadIdx.x + 32*threadIdx.y; i < FW2; i += 32)
@ -151,7 +153,8 @@ void density_est(float4 *pixbuf, float4 *outbuf, float *denbuf,
+ blockIdx.x * 32 + threadIdx.x + W2;
float4 in = pixbuf[idx];
float den = denbuf[idx];
float den;
read_pix(in, den);
if (in.w > 0 && den > 0) {
float ls = k1 * logf(1.0f + in.w * k2) / in.w;
@ -279,7 +282,7 @@ void density_est(float4 *pixbuf, float4 *outbuf, float *denbuf,
''')
def invoke(self, mod, cp, abufd, obufd, dbufd, stream=None):
def invoke(self, mod, cp, abufd, obufd, stream=None):
# TODO: add no-est version
# TODO: come up with a general way to average these parameters
@ -301,7 +304,7 @@ void density_est(float4 *pixbuf, float4 *outbuf, float *denbuf,
neg_est_curve = np.float32(-cp.estimator_curve)
est_min = np.float32(cp.estimator_minimum / 3.)
fun = mod.get_function("density_est")
fun(abufd, obufd, dbufd, est_sd, neg_est_curve, est_min, k1, k2,
fun(abufd, obufd, est_sd, neg_est_curve, est_min, k1, k2,
block=(32, 32, 1), grid=(self.features.acc_width/32, 1),
stream=stream)

View File

@ -16,13 +16,33 @@ class IterCode(HunkOCode):
bodies = [self._xfbody(i,x) for i,x in enumerate(self.features.xforms)]
bodies.append(iterbody)
self.defs = '\n'.join(bodies)
self.decls += self.pix_helpers.substitute(features=features)
decls = """
// Note: for normalized lookups, uchar4 actually returns floats
texture<uchar4, cudaTextureType2D, cudaReadModeNormalizedFloat> palTex;
__shared__ iter_info info;
"""
pix_helpers = Template("""
__device__
void read_pix(float4 &pix, float &den) {
den = pix.w;
{{if features.pal_has_alpha}}
read_half(pix.z, pix.w, pix.z, den);
{{endif}}
}
__device__
void write_pix(float4 &pix, float den) {
{{if features.pal_has_alpha}}
write_half(pix.z, pix.z, pix.w, den);
{{endif}}
pix.w = den;
}
""")
def _xfbody(self, xfid, xform):
px = self.packer.view('info', 'xf%d_' % xfid)
px.sub('xf', 'cp.xforms[%d]' % xfid)
@ -204,12 +224,17 @@ void iter(mwc_st *msts, iter_info *infos, float4 *accbuf, float *denbuf) {
float4 outcol = tex2D(palTex, color, {{packer.get("cp_step_frac")}});
float4 pix = accbuf[i];
float den;
// TODO: unify read/write_pix cycle when alpha is needed
read_pix(pix, den);
pix.x += outcol.x;
pix.y += outcol.y;
pix.z += outcol.z;
pix.w += outcol.w;
accbuf[i] = pix; // TODO: atomic operations (or better)
denbuf[i] += 1.0f;
den += 1.0f;
write_pix(pix, den);
accbuf[i] = pix;
}
}
''')

View File

@ -50,7 +50,7 @@ class BaseCode(HunkOCode):
#include<stdio.h>
"""
defs = """
defs = r"""
#undef M_E
#undef M_LOG2E
#undef M_LOG10E
@ -103,6 +103,39 @@ void zero_dptr(float* dptr, int size) {
dptr[i] = 0.0f;
}
}
__device__
void read_half(float &x, float &y, float xy, float den) {
asm("\n\t{"
"\n\t .reg .u16 x, y;"
"\n\t .reg .f32 rc;"
"\n\t mov.b32 {x, y}, %2;"
"\n\t mul.f32 rc, %3, 0f37800000;" // 1/65536.
"\n\t cvt.rn.f32.u16 %0, x;"
"\n\t cvt.rn.f32.u16 %1, y;"
"\n\t mul.f32 %0, %0, rc;"
"\n\t mul.f32 %1, %1, rc;"
"\n\t}"
: "=f"(x), "=f"(y) : "f"(xy), "f"(den));
}
__device__
void write_half(float &xy, float x, float y, float den) {
asm("\n\t{"
"\n\t .reg .u16 x, y;"
"\n\t .reg .f32 rc, xf, yf;"
"\n\t rcp.approx.f32 rc, %3;"
"\n\t mul.f32 rc, rc, 65536.0;"
"\n\t mul.f32 xf, %1, rc;"
"\n\t mul.f32 yf, %2, rc;"
"\n\t cvt.rni.u16.f32 x, xf;"
"\n\t cvt.rni.u16.f32 y, yf;"
"\n\t mov.b32 %0, {x, y};"
"\n\t}"
: "=f"(xy) : "f"(x), "f"(y), "f"(den));
}
"""
@staticmethod

View File

@ -229,7 +229,6 @@ class _AnimRenderer(object):
memset(byref(self._cen_cp), 0, sizeof(self._cen_cp))
self.nbins = anim.features.acc_height * anim.features.acc_stride
self.d_den = cuda.mem_alloc(4 * self.nbins)
self.d_accum = cuda.mem_alloc(16 * self.nbins)
self.d_out = cuda.mem_alloc(16 * self.nbins)
self.d_infos = cuda.mem_alloc(anim._iter.packer.align * self.ncps)
@ -245,8 +244,6 @@ class _AnimRenderer(object):
a._interp(cen_time, cen_cp)
palette = self._interp_colors(cen_time, cen_cp)
util.BaseCode.zero_dptr(a.mod, self.d_den, self.nbins,
self.stream)
util.BaseCode.zero_dptr(a.mod, self.d_accum, 4 * self.nbins,
self.stream)
@ -311,7 +308,7 @@ class _AnimRenderer(object):
# TODO: get block config from IterCode
# TODO: print timing information
iter_fun(self.d_seeds[b], np.uint64(d_info_off),
self.d_accum, self.d_den, texrefs=[tref],
self.d_accum, texrefs=[tref],
block=(32, 16, 1), grid=(len(block_times), 1),
stream=self.stream)
@ -327,8 +324,7 @@ class _AnimRenderer(object):
util.BaseCode.zero_dptr(a.mod, self.d_out, 4 * self.nbins,
self.stream)
a._de.invoke(a.mod, Genome(cen_cp),
self.d_accum, self.d_out, self.d_den,
a._de.invoke(a.mod, Genome(cen_cp), self.d_accum, self.d_out,
self.stream)
f = np.float32
@ -381,11 +377,6 @@ class _AnimRenderer(object):
g = a.features.gutter
obuf_dim = (a.features.acc_height, a.features.acc_stride, 4)
out = cuda.from_device(self.d_out, obuf_dim, np.float32)
#dacc = cuda.from_device(self.d_accum, obuf_dim, np.float32)
#daccw = dacc[:,:,3]
#print daccw.sum()
# TODO: performance?
g = a.features.gutter
out = np.delete(out, np.s_[:g], axis=0)
out = np.delete(out, np.s_[:g], axis=1)
out = np.delete(out, np.s_[-g:], axis=0)
@ -447,6 +438,10 @@ class Features(object):
else:
self.final_xform_index = None
alphas = np.array([c.color[3] for g in genomes
for c in g.palette.entries])
self.pal_has_alpha = np.any(alphas != 1.0)
self.max_cps = max([cp.ntemporal_samples for cp in genomes])
self.width = genomes[0].width