我正在用Numpy生成一个Meshgrid,它占用了大量内存,并且花费了很多时间。
xi, yi = np.meshgrid(xi, yi)
我正在生成与底层站点地图图像相同的分辨率的网状网格,有时尺寸为3000px。有时,它会使用几段内存,而将其写入页面文件时则需要10-15秒或更长时间。
我的问题是;我可以在不升级服务器的情况下加快速度吗?这是我的应用程序源代码的完整副本。
def generateContours(date_collected, substance_name, well_arr, site_id, sitemap_id, image, title_wildcard='', label_over_well=False, crop_contours=False, groundwater_contours=False, flow_lines=False, site_image_alpha=1, status_token=""):
#create empty arrays to fill up!
x_values = []
y_values = []
z_values = []
#iterate over wells and fill the arrays with well data
for well in well_arr:
x_values.append(well['xpos'])
y_values.append(well['ypos'])
z_values.append(well['value'])
#initialize numpy array as required for interpolation functions
x = np.array(x_values, dtype=np.float)
y = np.array(y_values, dtype=np.float)
z = np.array(z_values, dtype=np.float)
#create a list of x, y coordinate tuples
points = zip(x, y)
#create a grid on which to interpolate data
start_time = time.time()
xi, yi = np.linspace(0, image['width'], image['width']), np.linspace(0, image['height'], image['height'])
xi, yi = np.meshgrid(xi, yi)
#interpolate the data with the matlab griddata function (http://matplotlib.org/api/mlab_api.html#matplotlib.mlab.griddata)
zi = griddata(x, y, z, xi, yi, interp='nn')
#create a matplotlib figure and adjust the width and heights to output contours to a resolution very close to the original sitemap
fig = plt.figure(figsize=(image['width']/72, image['height']/72))
#create a single subplot, just takes over the whole figure if only one is specified
ax = fig.add_subplot(111, frameon=False, xticks=[], yticks=[])
#read the database image and save to a temporary variable
im = Image.open(image['tmpfile'])
#place the sitemap image on top of the figure
ax.imshow(im, origin='upper', alpha=site_image_alpha)
#figure out a good linewidth
if image['width'] > 2000:
linewidth = 3
else:
linewidth = 2
#create the contours (options here http://cl.ly/2X0c311V2y01)
kwargs = {}
if groundwater_contours:
kwargs['colors'] = 'b'
CS = plt.contour(xi, yi, zi, linewidths=linewidth, **kwargs)
for key, value in enumerate(CS.levels):
if value == 0:
CS.collections[key].remove()
#add a streamplot
if flow_lines:
dy, dx = np.gradient(zi)
plt.streamplot(xi, yi, dx, dy, color='c', density=1, arrowsize=3, arrowstyle='<-')
#add labels to well locations
label_kwargs = {}
if label_over_well is True:
label_kwargs['manual'] = points
plt.clabel(CS, CS.levels[1::1], inline=5, fontsize=math.floor(image['width']/100), fmt="%.1f", **label_kwargs)
#add scatterplot to show where well data was read
scatter_size = math.floor(image['width']/20)
plt.scatter(x, y, s=scatter_size, c='k', facecolors='none', marker=(5, 1))
try:
site_name = db_session.query(Sites).filter_by(site_id=site_id).first().title
except:
site_name = "Site Map #%i" % site_id
sitemap = SiteMaps.query.get(sitemap_id)
if sitemap.title != 'Sitemap':
sitemap_wildcard = " - " + sitemap.title
else:
sitemap_wildcard = ""
if title_wildcard != '':
filename_wildcard = "-" + slugify(title_wildcard)
title_wildcard = " - " + title_wildcard
else:
filename_wildcard = ""
title_wildcard = ""
#add descriptive title to the top of the contours
title_font_size = math.floor(image['width']/72)
plt.title(parseDate(date_collected) + " - " + site_name + " " + substance_name + " Contour" + sitemap_wildcard + title_wildcard, fontsize=title_font_size)
#generate a unique filename and save to a temp directory
filename = slugify(site_name) + str(int(time.time())) + filename_wildcard + ".pdf"
temp_dir = tempfile.gettempdir()
tempFileObj = temp_dir + "/" + filename
savefig(tempFileObj) # bbox_inches='tight' tightens the white border
#clears the matplotlib memory
clf()
#send the temporary file to the user
resp = make_response(send_file(tempFileObj, mimetype='application/pdf', as_attachment=True, attachment_filename=filename))
#set the users status token for javascript workaround to check if file is done being generated
resp.set_cookie('status_token', status_token)
return resp
最佳答案
如果meshgrid
是让您减速的原因,请不要调用它...根据 griddata
docs:
因此,如果您跳过对griddata
的调用并执行以下操作,则对meshgrid
的调用应与之相同:
xi = np.linspace(0, image['width'], image['width'])
yi = np.linspace(0, image['height'], image['height'])
zi = griddata(x, y, z, xi, yi, interp='nn')
这就是说,如果您的
x
和y
向量很大,则实际的插值(即对griddata
的调用)可能会花费相当长的时间,因为Delaunay三角剖分是一项计算密集型操作。您确定您的性能问题来自meshgrid
而不是griddata
吗?关于python - 加速Numpy Meshgrid命令,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/18200541/